Diego Prost

Franck Bielle

Keith L Ligon

MD Mehdi Touat
email: mehdi.touat@aphp.fr

Mutational burden and immune recognition of gliomas

Keywords: Biomarkers, immune checkpoints, immunotherapy, chemotherapy, immune microenvironment

Purpose of review

Recent evidence suggests high tumor mutational burden (TMB-H) as a predictor of response to immune checkpoint blockade (ICB) in cancer. However, results in TMB-H gliomas have been inconsistent. In this article, we discuss the main pathways leading to TMB-H in glioma and how these might affect immunotherapy response.

Recent findings

Recent characterization of TMB-H gliomas showed that "post-treatment hypermutation" related to mismatch repair (MMR) deficiency is the most common mechanism leading to TMB-H in gliomas. Unexpectedly, preliminary evidence suggested no benefit with ICB as compared to chemotherapy in this population. In contrast, ICB response was reported in a subset of TMB-H gliomas associated with constitutional MMR or polymerase epsilon (POLE) defects (e.g., constitutional biallelic MMRd deficiency). In other cancers, several trials suggest increased ICB efficacy is critically associated with increased lymphocyte infiltration at baseline which is missing in most gliomas. Further characterization of the immune microenvironment of gliomas is needed to identify biomarkers to select the patients who will benefit from ICB.

Summary

Intrinsic molecular and immunological differences between gliomas and other cancers might explain the lack of efficacy of ICB in TMB-H gliomas. Novel combinations and biomarkers are awaited to increase immunotherapy response in these cancers.

Introduction

Gliomas are the most common primary tumors of the central nervous system (CNS) [START_REF] Ostrom | Neuro-Oncology CBTRUS Statistical Report : Primary brain and other central nervous system tumors diagnosed in the United[END_REF].

They can affect patients of any age. They are frequently aggressive and responsible for high morbidity and mortality. The treatment of gliomas varies depending on accessibility for surgical resection, tumor grade and molecular profile. It typically includes radiation therapy and chemotherapy with alkylating agents such as temozolomide (TMZ) [START_REF] Wen | Glioblastoma in adults: a Society for Neuro-Oncology (SNO) and European Society of Neuro-Oncology (EANO) consensus review on current management and future directions[END_REF][START_REF] Weller | EANO guidelines on the diagnosis and treatment of diffuse gliomas of adulthood[END_REF][START_REF] Weller | European Association for Neuro-Oncology (EANO) guideline on the diagnosis and treatment of adult astrocytic and oligodendroglial gliomas[END_REF]. Despite these treatments, relapse is almost inevitable, especially in high-grade gliomas (HGG). Recurrent HGGs are among the most challenging cancers to treat, commonly harboring resistance to conventional, targeted therapies and immunotherapies [START_REF] Touat | Glioblastoma targeted therapy : updated approaches from recent biological insights[END_REF].

The development of immune checkpoint blockade (ICB) has recently transformed the care of various cancer types. Intensive efforts have focused on identifying predictive biomarkers for clinical response to ICBs. Among several markers under investigation, a number of studies showed a positive correlation between ICB response rates and the presence of a high tumor mutational burden (TMB-H), defined as the number of coding mutations per megabase (Mb) across the genome [START_REF] Chan | Development of tumor mutation burden as an immunotherapy biomarker: Utility for the oncology clinic[END_REF][START_REF] Cristescu | Pan-tumor genomic biomarkers for PD-1 checkpoint blockade-based immunotherapy[END_REF][START_REF] Yarchoan | Tumor Mutational Burden and Response Rate to PD-1 Inhibition[END_REF][START_REF] Rizvi | Cancer immunology. Mutational landscape determines sensitivity to PD-1 blockade in non-small cell lung cancer[END_REF][START_REF] Mcgranahan | Clonal neoantigens elicit T cell immunoreactivity and sensitivity to immune checkpoint blockade[END_REF][START_REF] Keenan | Genomic correlates of response to immune checkpoint blockade[END_REF]. These data as well as promising results from the Keynote-158 study led to the tumor-agnostic approval of the anti-PD1 pembrolizumab for TMB-H tumors by the Food and Drug Administration (FDA) in 2020 [START_REF] Marabelle | Association of tumour mutational burden with outcomes in patients with advanced solid tumours treated with pembrolizumab: prospective biomarker analysis of the multicohort, open-label, phase 2 KEYNOTE-158 study[END_REF]. However, the correlation between TMB and ICB clinical benefit was mainly driven by data from a limited number of cancers such as melanoma, lung carcinomas and known mismatch repair deficient (MMR-d) cancers, and it remains unclear whether TMB-H and MMR-d are universally predictive in rare cancers not represented in these studies [START_REF] Campbell | Retrospective pan-cancer analysis of TMB and mutational signatures across a variety of human pediatric and adult cancers. Analysis of the mechanisms responsible for TMB[END_REF]14]. Gliomas are one of such cancers, as these tumors typically harbor a strong immunosuppressive TME [START_REF] Thorsson | The Immune Landscape of Cancer[END_REF] and conflicting data has been reported regarding their benefit from ICB, even in the presence of TMB [START_REF] Gromeier | Very low mutation burden is a feature of inflamed recurrent glioblastomas responsive to cancer immunotherapy[END_REF][START_REF] Bouffet | Immune checkpoint inhibition for hypermutant glioblastoma multiforme resulting from germline biallelic mismatch repair deficiency[END_REF][18][19][20][21][22][23][24][25][26][27][28].

In this review, we discuss recent data on hypermutated gliomas, their mechanism of mutagenesis and the potential role of TMB-H as a prognostic and predictive biomarker for response to chemotherapy and immunotherapy.

TMB-H in gliomas: mechanisms and potential role in predicting prognosis and response to conventional therapies.

Cancer somatic mutations are caused by mutational processes of exogenous and endogenous origin which happen during development of each tumor cell and its progeny [START_REF] Alexandrov | Signatures of mutational processes in human cancer[END_REF][START_REF] Stratton | The cancer genome[END_REF][START_REF] Alexandrov | The repertoire of mutational signatures in human cancer[END_REF][START_REF] Vogelstein | Cancer Genome Landscapes[END_REF]. Each mutational process can involve components of DNA damage or modification, abnormal DNA replication or repair and generates a "mutational signature" (e.g., specific mutational pattern), which can include base substitutions, small insertions and deletions (indels), chromosome rearrangements and copy number abnormalities.

Mutational signatures can be extracted from tumor sequencing data (e.g., exome or genome sequencing) to infer the mutational processes responsible for mutations in individual samples. Mutations are sometimes associated with the production of foreign antigens (neoantigens) which are recognized by the immune system and can elicit T cell immunoreactivity.

The frequency of mutations and underlying mechanisms causing them varies greatly across cancers [START_REF] Campbell | Retrospective pan-cancer analysis of TMB and mutational signatures across a variety of human pediatric and adult cancers. Analysis of the mechanisms responsible for TMB[END_REF][START_REF] Jiricny | The multifaceted mismatch-repair system[END_REF]. A small subset of cancers (<20% of cancers) show a markedly elevated mutation burden which is referred to as TMB-H (or hypermutation, often used for some cancers like gliomas). The mutation burden defining this varies across assays used but is generally higher than 10 mutations per Mb of genome sequenced. Exceptionally (<1% of cancers), an "ultra-hypermutated" (i.e. TMB higher than 100 mutations per Mb) is observed [START_REF] Campbell | Retrospective pan-cancer analysis of TMB and mutational signatures across a variety of human pediatric and adult cancers. Analysis of the mechanisms responsible for TMB[END_REF]. TMB-H is prevalent in melanoma [START_REF] Hugo | Genomic and Transcriptomic Features of Response to Anti-PD-1 Therapy in Metastatic Melanoma[END_REF] and lung cancer [START_REF] Rizvi | Molecular determinants of response to antiprogrammed cell death (PD)-1 and anti-programmed death-ligand 1 (PD-L1) blockade in patients with non-small-cell lung cancer profiled with targeted next-generation sequencing[END_REF], where the increase in TMB is mainly related to environmental mutagens exposure (tobacco smoke, UV light), and associated with ICB response [START_REF] Miao | Genomic correlates of response to immune checkpoint blockade in microsatellite-stable solid tumors[END_REF]. In gliomas, TMB-H is less common and observed in two distinct contexts associated with unique biology: de novo (i.e., hypermutation present in the newly-diagnosed tumor) and posttreatment (i.e. hypermutation only found at recurrence after treatment).

De novo hypermutation

De novo hypermutation is found in less than 2% of all newly-diagnosed gliomas [14]. De novo hypermutation in gliomas has been reported in tumors with inherited or somatic defects of the DNA polymerases ε (POLE) and δ (POLD1) or the MMR system, which lead to the loss of polymerase proofreading or DNA replication error repair, respectively (Figure 1). Given its rarity and lack of dedicated prospective trials focusing on these patients, the management of gliomas in patients with de novo TMB-H glioma is not well codified [START_REF] Alnahhas | Management of gliomas in patients with Lynch syndrome[END_REF].

DNA replication fidelity is primarily governed by the DNA polymerases POLE and POLD1 catalytic and proofreading domains. Germline pathogenic mutations in the exonuclease domains of polymerases POLE and POLD1 predispose to adenomatous polyps, colorectal cancer (CRC), endometrial cancer, and more rarely to other malignancies including glioblastoma [26,[START_REF] Vande Perre | Germline mutation p.N363K in POLE is associated with an increased risk of colorectal cancer and giant cell glioblastoma[END_REF], all of which are typically harboring hypermutation or ultra-hypermutation [START_REF] Campbell | Retrospective pan-cancer analysis of TMB and mutational signatures across a variety of human pediatric and adult cancers. Analysis of the mechanisms responsible for TMB[END_REF]. Somatic POLE defects have also been reported in glioblastoma [START_REF] Erson-Omay | Somatic POLE mutations cause an ultramutated giant cell high-grade glioma subtype with better prognosis[END_REF]. Very little is known about the phenotype of POLE/POLD1deficient gliomas. Recent studies have suggested an association between POLE/POLD1 defects, increased inflammatory infiltrates, and longer survival in gliomas, but these data need further confirmation in larger datasets [START_REF] Pollo | GIANT CELL GLIOBLASTOMAS: ANALYSIS OF MISMATCH-REPAIR (MMR) PROTEINS EXPRESSION, POLIMERASE ε (POLE) MUTATIONS AND THEIR ROLE IN TUMOR IMMUNORESPONSE[END_REF].

The MMR system -consisting mainly of MSH2, MSH6, MLH1 and PMS2 proteins replication and recruiting proteins which excise the newly-synthetized strand before DNA is resynthesized by DNA polymerases [START_REF] Jiricny | The multifaceted mismatch-repair system[END_REF]. Germline -and less commonly somatic -MMR defects have both been reported in de novo hypermutated gliomas. Constitutional (Biallelic) mismatch repair deficiency (CMMR-d) is a rare autosomal recessive disorder caused by germline biallelic MMR mutations, most commonly affecting PMS2, and characterized by early-onset cancers. Gliomas are one of the tumors commonly seen in CMMR-d patients [26,[START_REF] Bakry | Genetic and clinical determinants of constitutional mismatch repair deficiency syndrome: report from the constitutional mismatch repair deficiency consortium[END_REF][START_REF] Aronson | Diagnostic criteria for constitutional mismatch repair deficiency (CMMRD): recommendations from the international consensus working group[END_REF][START_REF] Guerrini-Rousseau | Constitutional mismatch repair deficiencyassociated brain tumors: report from the European C4CMMRD consortium[END_REF][START_REF] Lavoine | Constitutional mismatch repair deficiency syndrome: clinical description in a French cohort[END_REF][START_REF] Vasen | Guidelines for surveillance of individuals with constitutional mismatch repair-deficiency proposed by the European Consortium "Care for CMMR-D" (C4CMMR-D)[END_REF]. They develop at younger age (<10 years). The histology is most commonly glioblastomas which are wild-type for other common defining driver events such as H3F3A, IDH1/2, or infant-type receptor tyrosine kinase (RTK) aberrations. The prognosis of CMMR-d patients is poor, especially once patients develop brain tumors. In a subset of patients with CMMR-d glioma, secondary hits in the polymerase POLE/POLD1 are acquired, leading to a rapid burst in the mutational burden (ultra-hypermutation) (Figure 1) [START_REF] Campbell | Retrospective pan-cancer analysis of TMB and mutational signatures across a variety of human pediatric and adult cancers. Analysis of the mechanisms responsible for TMB[END_REF][START_REF] Shlien | Combined hereditary and somatic mutations of replication error repair genes result in rapid onset of ultra-hypermutated cancers[END_REF]. Lynch syndrome is an autosomal dominant disorder caused by germline heterozygous inactivating mutations of one of the MMR genes. Patients with Lynch syndrome can develop cancers after a second hit occurring in the remaining wild-type MMR allele leading to MMR loss of function, which typically occurs after the first decade of life. Patients with Lynch syndrome most commonly develop colorectal, urinary, or gynecological cancers but can also suffer from high-grade glioma [START_REF] Dodgshun | Germline-driven replication repair-deficient high-grade gliomas exhibit unique hypomethylation patterns[END_REF][START_REF] Therkildsen | Glioblastomas, astrocytomas and oligodendrogliomas linked to Lynch syndrome[END_REF]. Most gliomas arising in patients with Lynch syndrome are IDH1/2-wild-type glioblastomas and seem to have a poor prognosis, although IDH1/2-mutant astrocytomas with MMR-d have also been reported [START_REF] Dodgshun | Germline-driven replication repair-deficient high-grade gliomas exhibit unique hypomethylation patterns[END_REF][START_REF] Suwala | Primary mismatch repair deficient IDH-mutant astrocytoma (PMMRDIA) is a distinct type with a poor prognosis[END_REF].

Post-treatment hypermutation

Post-treatment hypermutation is the most common cause of TMB-H in gliomas, ranging from 5-60% of gliomas depending on tumor subclass, genetics, and treatment history [START_REF] Hunter | A Hypermutation Phenotype and Somatic MSH6 Mutations in Recurrent Human Malignant Gliomas after Alkylator Chemotherapy[END_REF][START_REF] Yu | Temozolomide-induced hypermutation is associated with distant recurrence and reduced survival after high-grade transformation of lowgrade IDH-mutant gliomas[END_REF]. Post-treatment hypermutation is predominantly seen in gliomas which are known to be the most responsive to chemotherapy [14, [START_REF] Hunter | A Hypermutation Phenotype and Somatic MSH6 Mutations in Recurrent Human Malignant Gliomas after Alkylator Chemotherapy[END_REF][52][START_REF] Yip | MSH6 mutations arise in glioblastomas during temozolomide therapy and mediate temozolomide resistance[END_REF][START_REF] Johnson | Longitudinal genomic analysis of low-grade gliomas showing common development of TMB-H after treatment with TMZ in this population[END_REF][55][START_REF] Caccese | Mismatch-repair protein expression in high-grade gliomas: A large retrospective multicenter study[END_REF]. TMZ is an alkylating agent widely used to treat gliomas. Its mechanism of action is based on the production of an intermediate metabolite reaching high concentration in the brain and producing methyl groups in tumor cells DNA, particularly on N7 and O6 guanines residues [START_REF] Dunn | Emerging immunotherapies for malignant glioma: From immunogenomics to cell therapy[END_REF]. The enzyme O6-methylguanine DNA methyltransferase (MGMT) removes the O6 guanine methyl groups (O6-meG) which are the most cytotoxic lesions [START_REF] Fu | SERIES: Genomic instability in cancer Balancing repair and tolerance of DNA damage caused by alkylating agents[END_REF]. The enzyme is a "suicide" protein and each MGMT protein can only repair one O6-meG residue on DNA, which means the levels of MGMT protein in cells is critical to DNA repair. MGMT promoter methylation, which silences its expression, leads to an MGMT-deficient state (MGMT-d), and is associated with increased sensitivity to TMZ and improved prognosis in patients with glioma [START_REF] Esteller | INACTIVATION OF THE DNA-REPAIR GENE MGMT AND THE CLINICAL RESPONSE OF GLIOMAS TO ALKYLATING AGENTS[END_REF][START_REF] Hegi | MGMT Gene Silencing and Benefit from Temozolomide in Glioblastoma[END_REF].

In the absence of O6-meG removal (e.g. in MGMT-d tumors), replication of O6-meG-containing DNA results in the insertion of a thymine opposite the O6-meG, creating a O6-meG:T mismatch that is recognized by the MMR machinery. Failed attempts to repair O6-meG:T mismatch by MMR generate DNA strand breaks, ultimately leading to cell cycle arrest and cell death. This means that TMZ cytotoxicity is critically dependent on a functional MMR pathway. Consequently, MMR-d cells (e.g. cells lacking MMR capacity due to mutations in genes encoding MMR proteins) display resistance to alkylating agents such as TMZ [14].

MMR-d cells have increased burden of mutations of several types. Single base substitutions are the most common and are the mutation type reported in "TMB" most commonly calculated from sequencing. In addition, MMR deficiency also results in mutations (e.g. indels) at tandemly repeated DNA motifs (microsatellites) which lead to microsatellite instability (MSI), a well-known and widely used marker to diagnose MMR deficiency in common MMR-d cancers such as colorectal cancer [START_REF] Ratovomanana | Performance of Next Generation Sequencing for the Detection of Microsatellite Instability in Colorectal Cancer with Deficient DNA Mismatch Repair[END_REF]. The degree to which the MSI/indel repair and MMR are linked in TMB-H cancers is not well understood and in the most common MMR-d cancers they co-occur in almost all cases.

In gliomas, TMZ-induced DNA damage and hypermutation is now known to be characterized by the acquisition of MMR-d mutations or other alterations but shows a lack of MSI or significantly increased indels. They also harbor a unique MMR-d mutational signature (signature 11) specific to TMZ in a setting of cells which cannot repair TMZ-related mismatches due to MMR deficiency. Interestingly, MMR-d gliomas with TMB-H also lack significant inflammatory CD8 + infiltrates compared to the most common MMR-d cancers [14, [START_REF] Indraccolo | Genetic, epigenetic, and immunologic profiling of MMR-deficient relapsed glioblastoma[END_REF][START_REF] Hodges | Mutational burden, immune checkpoint expression, and mismatch repair in glioma: Implications for immune checkpoint immunotherapy[END_REF][START_REF] Kloor | The Immune Biology of Microsatellite-Unstable Cancer[END_REF], even when the latter are located in the CNS [START_REF] Sun | Genomic signatures reveal DNA damage response deficiency in colorectal cancer brain metastases[END_REF][START_REF] Dunn | Mismatch Repair Deficiency in High-Grade Meningioma: A Rare but Recurrent Event Associated With Dramatic Immune Activation and Clinical Response to PD-1 Blockade[END_REF].

Origins of MMR-d cells in post-treatment gliomas and clinical implications

The highest rates of TMB-H have been reported in the most chemosensitive subtypes where MGMT promoter methylation is more common (e.g., IDH1/2-mutant astrocytomas and oligodendrogliomas). While recent studies help to define post-treatment TMB-H gliomas as an MMR-d cancer, a question that remains unaddressed is whether preexisting MMR-d cells are selected for after treatment response or whether the initial MMR mutations are induced by TMZ in cells and selected for during treatment, or a combination of both processes. Although it is difficult to ascertain the origins of posttreatment MMR deficiency in individual samples, indirect data suggests that in a subset of samples TMZ induces mutations which cause MMR-d in cells. This is for instance showed by the fact that the MMR-d inducing hotspot mutation most frequently found in post-treatment hypermutated gliomas (~15%) is an MSH6 T1219I mutation with dominant negative effect found exceptionally in patients with Lynch syndrome [START_REF] Berends | Molecular and clinical characteristics of MSH6 variants: An analysis of 25 index carriers of a germline variant[END_REF][START_REF] Yang | Dominant effects of an Msh6 missense mutation on DNA repair and cancer susceptibility[END_REF][69][START_REF] Huang | Pathogenic germline variants in 10,389 adult cancer[END_REF][START_REF] Fiala | Prospective pan-cancer germline testing using MSK-IMPACT informs clinical translation in 751 patients with pediatric solid tumors[END_REF].

This variant results from a C > T transition similar to TMZ-associated lesions and is inducible in in vitro models chronically exposed to TMZ [14].

Conflicting data has been reported regarding the prognosis of post-treatment hypermutation. While the GLASS study found no prognostic significance [START_REF] Caccese | Mismatch-repair protein expression in high-grade gliomas: A large retrospective multicenter study[END_REF][START_REF] Glass) Consortium | LONGITUDINAL MOLECULAR TRAJECTORIES OF DIFFUSE GLIOMA IN ADULTS[END_REF], two retrospective studies suggested that post-treatment hypermutated might have a worse prognosis from recurrence when compared to non-hypermutated recurrences. However, since secondary MMR defects occur in tumors most sensitive, and potentially with the greatest beneficial responses to TMZ, the deleterious effect of secondary MMR deficiency (poor prognosis after relapse) is unlikely to outweigh its positive effects. These results therefore do not argue for the use of TMZ vs nitrosourea-based protocols (e.g. PCV) in lower grade gliomas, especially given that randomized trial data demonstrated survival benefit with TMZ in both IDH1/2-wild-type and -mutant tumors [START_REF] Van Den Bent | Adjuvant and concurrent temozolomide for 1p/19q non-co-deleted anaplastic glioma (CATNON; EORTC study 26053-22054): second interim analysis of a randomised, open-label, phase 3 study[END_REF][START_REF] Stupp | Radiotherapy plus Concomitant and Adjuvant Temozolomide for Glioblastoma[END_REF].

Regarding treatment response, while data regarding radiation therapy or chemoradiation is currently insufficient [START_REF] Martin | DNA mismatch repair and the DNA damage response to ionizing radiation: making sense of apparently conflicting data[END_REF], consistent evidence shows that MMR-d or TMB-H in gliomas are both predictive biomarkers for resistance to single-agent TMZ.

Interestingly, experimental data from models and indirect evidence from clinical samples suggest that at least a subset of MMR-d tumors might retain sensitivity to nitrosoureas such as CCNU [14, [START_REF] Dunn | Emerging immunotherapies for malignant glioma: From immunogenomics to cell therapy[END_REF][START_REF] Wedge | Potentiation of temozolomide and BCNU cytotoxicity by O6-benzylguanine: A comparative study in vitro[END_REF][START_REF] Wedge | 3-Aminobenzamide and/or O6-benzylguanine evaluated as an adjuvant to temozolomide or BCNU treatment in cell lines of variable mismatch repair status and O6-alkylguanine-DNA alkyltransferase activity[END_REF]. This observation might explain at least in part the superiority of the TMZ/CCNU combination with radiation compared to standard chemoradiation with TMZ recently reported in a randomized trial of newly-diagnosed MGMT-d glioblastomas [START_REF] Herrlinger | Lomustine-temozolomide combination therapy versus standard temozolomide therapy in patients with newly diagnosed glioblastoma with methylated MGMT promoter (CeTeG/NOA-09): a randomised, open-label, phase 3 trial[END_REF]. Further research is needed to address whether the TMZ/CCNU combination or PCV might reduce the risk of post-treatment hypermutation and to characterize the unique resistance mechanisms associated with this combination.

Another area of ongoing investigation is whether PARP inhibition might restore TMZ sensitivity in MMR-d glioma cells and therefore prevent the development of posttreatment hypermutation [START_REF] Higuchi | Restoration of temozolomide sensitivity by PARP inhibitors in mismatch repair deficient glioblastoma is independent of base excision repair[END_REF].

Treatment of hypermutated gliomas with ICB

The concept that TMB-H tumors are capable of presenting immunogenic neoantigens is well established [START_REF] Chan | Development of tumor mutation burden as an immunotherapy biomarker: Utility for the oncology clinic[END_REF]. Neoantigens are recognized and processed by dendritic cells which recruit lymphocytes against tumor neoantigens. In this context, ICB treatment enables lymphocyte proliferation (anti-CTLA-4) and prevents lymphocyte inactivation (anti-PD-1/PDL-1). Melanoma [START_REF] Snyder | Genetic Basis for Clinical Response to CTLA-4 Blockade in Melanoma[END_REF], NSCLC [START_REF] Garon | Pembrolizumab for the Treatment of Non-Small-Cell Lung Cancer[END_REF] and MMR-d tumors with MSI [START_REF] Le | Mismatch-repair deficiency predicts response of solid tumors to PD-1 blockade[END_REF] are the classic examples of TMB-H benefiting from ICB, but clinical data in hypermutated glioma as well as other cancer types has been so far inconsistent. Research for biomarkers predicting ICB response in the context of hypermutation is an area of intensive investigation [START_REF] Keenan | Genomic correlates of response to immune checkpoint blockade[END_REF][START_REF] Samstein | Tumor mutational load predicts survival after immunotherapy across multiple cancer types[END_REF][START_REF] Cho | Genomic correlates of response to CTLA-4 blockade in metastatic melanoma[END_REF]. A recent pan-cancer study was able to categorize TMB-H tumors in two groups with distinct pattern of ICB response [START_REF] Mcgrail | High tumor mutation burden fails to predict immune checkpoint blockade response across all cancer types[END_REF]. The first group, enriched with ICB responders, consisted of tumors in which increased TMB was associated with a great number of CD8 + lymphocytes infiltrates. In contrast, the second group showed no correlation between increased TMB and CD8 + infiltration. Of note, the latter group represents the majority of cancers including TMB-H gliomas [START_REF] Gromeier | Very low mutation burden is a feature of inflamed recurrent glioblastomas responsive to cancer immunotherapy[END_REF]. These important results clearly indicate TMB is not a universal predictive marker and suggests that additional biomarkers are required to appropriately select the patients most likely to benefit from immunotherapy.

Current data in de novo and post-treatment hypermutated gliomas

ICBs as a treatment has not shown improvement compared to standard of care in newlydiagnosed and recurrent glioblastomas, although the majority of patients included in these trials were TMB-low gliomas [START_REF] Reardon | Effect of Nivolumab vs Bevacizumab in patients with recurrent glioblastoma: the checkmate 143 phase 3 randomized clinical trial[END_REF]. Unfortunately, similar results have been observed even in TMB-H gliomas now. Indeed, while reports suggested that a subset of hypermutated gliomas might benefit from ICB [START_REF] Bouffet | Immune checkpoint inhibition for hypermutant glioblastoma multiforme resulting from germline biallelic mismatch repair deficiency[END_REF], recent retrospective analyses of hypermutated or MMR-d gliomas -mostly post-treatment -treated with anti-PD1 suggested that the use of ICB does not translate into clinical benefit (Table 1) [14,24].

Nevertheless, given their retrospective nature, further confirmation of these results in prospective studies is warranted (NCT03718767, NCT02658279, NCT04145115).

In contrast, in de novo TMB-H gliomas ICB has shown encouraging results reported in series studies [START_REF] Bouffet | Immune checkpoint inhibition for hypermutant glioblastoma multiforme resulting from germline biallelic mismatch repair deficiency[END_REF]20] and in several case reports [START_REF] Bouffet | Immune checkpoint inhibition for hypermutant glioblastoma multiforme resulting from germline biallelic mismatch repair deficiency[END_REF]19,21,22,[26][27][28]]. These findings were confirmed in a recent non-peer reviewed pre-print [20]. In this study, the authors analyzed the responses to ICBs of pediatric CMMR-d patients, including patients with glioma. Interestingly, in a subset of tumors with additional POLE/POLD1 defects, significant recruitment of inflammatory CD8 + cells and ICB benefit was observed. Even though CMMR-d gliomas response to ICBs was lower than in other tumor types developed in the same patients, it remained in appearance superior to the one of TMBlow gliomas [20].

Potential explanations for the low response rates in gliomas

A number of unique characteristics of hypermutated gliomas with other MMR-deficient tumors could at least in part explain the lack of response to ICB. First, the lack of clonal MSI and predominantly subclonal mutational burden of gliomas with post-treatment hypermutation could be associated with the absence of effective immune responses against tumor neoantigens [START_REF] Mcgranahan | Clonal neoantigens elicit T cell immunoreactivity and sensitivity to immune checkpoint blockade[END_REF]14,[START_REF] Samstein | Tumor mutational load predicts survival after immunotherapy across multiple cancer types[END_REF][START_REF] Gejman | Rejection of immunogenic tumor clones is limited by clonal fraction[END_REF]. Interestingly, patients with CMMR-d are more likely to harbor POLE/POLD1 defects which lead to ultra-hypermutation and accumulation of indels which are much more immunogenic neoantigens [START_REF] Hodel | Explosive mutation accumulation triggered by heterozygous human Pol ɛ proofreading-deficiency is driven by suppression of mismatch repair[END_REF] (Table 1). This might explain the presence of CD8 + cells expressing PDL-1 and increased rate of benefit from ICB in this setting. Furthermore, the absence of significant T lymphocyte infiltrates and ICB response even in some gliomas with de novo MMR-d gliomas (Lynch syndrome) suggest that beyond the nature of tumor neoantigens, specificities in the immunosuppressive microenvironment of gliomas -especially in the population of immunosuppressive microglial and macrophage cells which are the dominant immune TME cell types in glial tumors [START_REF] Thorsson | The Immune Landscape of Cancer[END_REF] -contribute significantly to gliomas ICB resistance. A proposed mechanism of resistance in non-responders derived from the study of preclinical models is the expansion of Treg (FOX3P + ) and macrophages in the tumor microenvironment [START_REF] Aslan | Heterogeneity of response to immune checkpoint blockade in hypermutated experimental gliomas[END_REF]. In this study, increased CD8 + infiltrates and INF-γ signaling was observed in the responders, suggesting that additional biomarkers might enable further subgrouping hypermutated gliomas and identifying ICB responders. The benefit of neoadjuvant PD1 inhibitors may support this as surgery is known to increase the levels of macrophages within the tumors.

Conclusions

Recent studies have improved our understanding of the mechanisms responsible for TMB-H in gliomas and its potential role as prognostic and predictive biomarker. Efforts are ongoing to determine the optimal strategy for use of radiation therapy and chemotherapy in the context of TMB-H. Areas of investigation include the development of non-invasive biomarkers to monitor hypermutation and the investigation of novel therapeutic strategies that will prevent MMR-d acquisition in the most chemosensitive such as oligodendrogliomas (e.g. by using CCNU or PARP inhibition in combination with TMZ) to determine whether preventing TMB-H development might improve patients outcome. As regard immunotherapy strategies, response and clinical benefit is driven by a sum of complex factors which cannot be explained only with the number of mutations in tumor exomes. Neoantigen quality seems determinant to responses as well as the presence of effectors immune cells in the TME. Approaches aimed at increasing both tumor infiltration by cytotoxic lymphocytes are therefore likely both necessary in order to improve the response to immunotherapy in gliomas. Among several current strategies under investigation, IL-12 gene therapy combined with ICB showed safety and biological efficacy (production of IFN-γ) in HGG patients including one patient with post-treatment hypermutation [22,[START_REF] Chiocca | Regulatable interleukin-12 gene therapy in patients with recurrent high-grade glioma: Results of a phase 1 trial[END_REF].

Key points

TMB-H in gliomas is observed in two distinct contexts associated with unique biology: de novo and post-treatment.

De novo TMB-H is observed in tumors with inherited or somatic defects of the DNA polymerases POLE/POLD1 or the MMR system.

24.

Lombardi G, Barresi V, Indraccolo

Figures and tables legends

4 *

 4 TMZ together with MMR-d is responsible for TMB-H and resistance in post-treatment gliomas.TMB-H MMR-d gliomas harbor unique characteristics (e.g., low lymphocyte infiltration) compared to other cancers where MMR-d is common.ICBs response in TMB-H is uncommon except in rare contexts such as CMMR-d. Lukas, R; Rodon, J; Becker K et al. Clinical activity and safety of atezolizumab in patients with recurrent glioblastoma. J Neurooncol. 2018;Nov(140(2)):317-28. * Phase I trial data with atezolizumab (anti-PD-L1) in recurrent glioblastoma. Clinical benefit observed in a TMB-H tumor with POLE-deficiency. 19. Sathornsumetee, S; Nunta-aree, S ;Cheunsuchon, P et al. Immune checkpoint inhibitor in recurrent hypermutated glioblastoma with POLE mutation. Neuro-Oncology Adv. 2021;vdab093. * Case report of a patient with TMB-H (POLE deficient) high-grade glioma patient with response to ICB. 20. Morgenstern, D; Sudhaman, S; Das A et al. Mutation and Microsatellite Burden Predict Response to PD-1 Inhibition in Children with Germline DNA Replication Repair Deficiency. ResearchSquare. (416):1-40. 21. Rittberg R, Harlos C, Rothenmund H, et al. Immune checkpoint inhibition as primary adjuvant therapy for an IDH1-mutant anaplastic astrocytoma in a patient with CMMRD: A case report-usage of immune checkpoint inhibition in CMMRD. Curr Oncol. 2021;28(1):757-66. 22. McCord, M; Lukas, R; Amidei C. Disappearance of MMR-deficient subclones after Controlled IL-12 and PD-1 inhibition in a glioma patient. Neuro-Oncology Adv [Internet]. 2021;vdab045:1-31. Available from: https://doi.org/10.1093/noajnl/vdab045 23. Anghileri E, Di Ianni N, Paterra R, et al. High tumor mutational burden and T-cell activation are associated with long-term response to anti-PD1 therapy in Lynch syndrome recurrent glioblastoma patient. Cancer Immunol Immunother [Internet]. 2021;70(3):831-42. Available from: https://doi.org/10.1007/s00262-020-02769-Case report of a patient with de novo TMB-H (POLE-deficient) high-grade glioma patient with response to ICB.

Figure 1 .

 1 Figure 1. Characteristics associated with de novo (top) and post-treatment (bottom) TMB-H in gliomas. Frequency and distribution across ages represent adults/adolescents/infants. De novo TMB-H tumors are rare and related to young patients. In these tumors, the driver MMR/POLE mutations can be inherited or somatic.TMB-H is found in the newly-diagnosed tumor. The combination of increased TMB, increased indels burden (often observed in POLE-deficient tumors), and increased tumor infiltration by T cells make these tumors more likely to benefit from ICBs, although the relative contribution of each individual factor is unknown. Post-treatment TMB-H tumors are strongly related to the use of TMZ in chemotherapy sensitive tumors (eg MGMT-d).TMB-H is only found in the recurrent (post-chemotherapy) tumor. Increased tumor infiltration and ICB response in this context are both rare.

  Clinical benefit with combined bevacizumab and pembrolizumab Higher TMB, indel burden, T-cell infiltration and PDL1 expression in tumors with combined MMR-d and POLE-d as compared to MMR-d only tumors De novo (5) and post-treatment (6) TMB-H samples Loss of MMR-d clones after local IL-12 and anti-PD-1 combination therapy Significantly less response seen compared to POLE-deficient cases Neither TMB nor CD8+ T-cell infiltration associated with pembrolizumab activity CMMR-d patient CMMR-d patient Tumor sequencing data not available. 2 Lynch and 2 CMMR-d patients

report of a patient with de novo TMB-H (POLE-deficient) high-grade glioma patient with response to ICB.

						S, et al. Pembrolizumab activity in recurrent high-grade
	gliomas with partial or complete loss of mismatch repair protein expression: A monocentric,
	observational and prospective pilot study. Cancers (Basel). 2020;12(8):1-14.
	25.	Guo X, Wang S, Wang Y MW. Anti-PD-1 plus anti-VEGF therapy in multiple intracranial
	metastases	of	a	hypermutated,	IDH	wild-type	glioblastoma.	Neuro	Oncol.
	2021;Apr(12;23(4)):699-701.
	26.	Johanns TM, Miller CA, Dorward IG, et al. Immunogenomics of Hypermutated
	Glioblastoma: a Patient with Germline POLE Deficiency Treated with Checkpoint Blockade
	Immunotherapy. Cancer Discov. 2017;6(11):1230-6.
	27.	AlHarbi M, Ali Mobark N, AlMubarak L, et al. Durable Response to Nivolumab in a
	Pediatric Patient with Refractory Glioblastoma and Constitutional Biallelic Mismatch Repair
	Deficiency. Oncologist. 2018;23(12):1401-6.

* Case * Case

report of a patient with de novo TMB-H high-grade glioma patient with response to ICB.

	28.	Larouche V, Atkinson J, Albrecht S, et al. Sustained complete response of recurrent
	glioblastoma to combined checkpoint inhibition in a young patient with constitutional mismatch
	repair deficiency. Pediatr Blood Cancer. 2018;65(12):4-5.

Table 1 . Case reports and series of TMB-H gliomas and CNS tumors treated with ICB and other immunotherapy approaches.

 1

	Abbreviations: IDH1/2-mut, IDH1/2-mutant; MMR-d, MMR-deficient; POLE-d, POLE-
	deficient; TMZ, temozolomide; RT, radiation therapy; PFS, progression free survival; OS,
	overall survival; na, not available

§ Defined by prolonged disease control or radiological response as assessed by authors.

A subset of patients in the Morgenstern et al. study

[20]

showed tumor control after initial flare. † Post-nivolumab progression data from patient reported in the Bouffet et al. 2016 study

[START_REF] Bouffet | Immune checkpoint inhibition for hypermutant glioblastoma multiforme resulting from germline biallelic mismatch repair deficiency[END_REF]

. † † POLE deficiency assessed based on mutational signature analysis. PFS of 9.9 months and OS of 21.6 months reported for the overall dataset. * PFS and OS not available for POLE-deficient vs POLE-proficient cases. PFS of 9.9 months and OS of 21.6 months reported for the overall dataset.

Table 1 .Case reports and series of TMB-H gliomas and CNS tumors treated with ICB and other im

 1 § Defined by prolonged disease control or radiological response as assessed by authors. A subset o † Post-nivolumab progression data from patient reported in the Bouffet et al. 2016 study [17]. † † POLE deficiency assessed based on mutational signature analysis. of patients in the Tabori et al. study [20] showed tumor control after init of 21.6 months reported for the overall dataset. Z, temozolomide; RT, radiation therapy; PFS, progression free survival; O Notes Both patients had combined MMR-d and POLE-d (CMMR-d); one of patients is included in Larouche et al. [86] Patient with germline POLE deficiency Response to combined nivolumab and ipilimumab after progression on nivolumab De novo TMB-H patient with high lymphocyte infiltration and high burden of clonal variants in both primary and recurrent tumor samples

	* PFS and OS not available for POLE-deficient vs POLE-proficient cases. PFS of 9.9 months and OS o
	Abbreviations: IDH1/2-mut, IDH1/2-mutant; MMR-d, MMR-deficient; POLE-d, POLE-deficient; TMZ
	Study	IDH1/2-mut	MMR-d	Stage	Prior TMZ
	POLE-deficient
	[17] Bouffet et al. 2016 (n=2)	0 (0%)	2 (100%)	Recurrence	1 (50%)
	[26] Johanns et al. 2017 (n=1)	0 (0%)	NA	Recurrence	1 (100%)
	[28] Larouche et al. 2018 (n=1) †	0 (0%)	1 (100%)	Recurrence	1 (100%)
	[27] Anghileri et al. 2021 (n=1) † †	0 (0%)	1 (100%)	Recurrence	1 (100%)
	[19] Sathornsumetee et al. 2021 (n=1)	0 (0%)	NA	Recurrence	1 (100%)
	[20] Morgenstern et al. 2021 (n=19)	na	19 (100%)	na	na
	POLE-proficient
	[14] Touat et al. 2020 (n=11)	3 (27.2%)	11 (100%)	Recurrence	11 (100%)
	[22] McCord et al. 2021 (n=1)	1 (100%)	1 (100%)	Recurrence	1 (100%)
	[20] Morgenstern et al. 2021 (n=8)	na	8 (100%)	na	na
	POLE status na
	[24] Lombardi et al. 2020 (n=13)	4 (30.7%)	13 (100%)	na	13 (100%)
	[21] Rittberg et al. 2021 (n=1)	1 (100%)	1 (100%)	Primary	0 (0%)
	[27] Alharbi et al. 2018 (n=1)	na	1 (100%)	Recurrence	1 (100%)
	[20] Morgenstern et al. 2021 (n=4)	na	4 (100%)	na	na

Acknowledgements

None

Financial support and sponsorship

None.

Conflict of interest


D Loyal
email: loyald@hotmail.fr

Ab

A-L Sutter
email: alsutter@ch-perrens.fr

N Ac , Rascle

CHANGES IN MOTHERING IDEOLOGY AFTER CHILDBIRTH 1

Keywords: intensive mothering ideology, mothers, parental attitudes, parental role, postpartum

The prevailing dominant discourse about motherhood in western societies reflects a set of interconnected beliefs referred to as intensive mothering ideology. Little is known about how intensive mothering ideology changes after childbirth, and the associations between intensive mothering ideology and maternal psychological health. The current study aims to explore how intensive mothering ideology may evolve after childbirth in both primiparous and multiparous women, and whether any observed changes in this ideology impact maternal psychological health. French women (n = 144) completed a set of study measures during late pregnancy and then again at two months and four months postpartum, which assessed intensive mothering ideology, postpartum depression, and maternal burnout symptoms. As expected, the results indicated that intensive mothering ideology increases after childbirth. However, changes in ideology were not stronger in primiparous women compared to multiparous women. Of note, multiparous women reported stronger challenge and sacrifice beliefs. Finally, linear mixed models showed that changes in intensive mothering ideology were associated with maternal psychological health in contradictory ways, while controlling for parity and unemployment.

Mainly, growth in sacrificial beliefs seems to be detrimental to maternal psychological health.

These findings have implications for the well-being of mothers after childbirth and call for challenging the self-sacrifice beliefs that underpin intensive mothering ideology and promoting self-care.

Changes in Mothering Ideology After Childbirth and Maternal Psychological Health in French Women

According to the World Health Organization, women's psychological health cannot be disconnected from their roles in societies (WHO, 1993). Similarly, various scholars have argued that mothers' experiences cannot be understood without considering existing gender ideologies [START_REF] Arendell | Conceiving and investigating motherhood: The decade's scholarship[END_REF]. Many studies have been conducted on the role of gender ideologies [START_REF] Davis | Gender ideology: Components, predictors, and consequences[END_REF]; however, less is known about specific beliefs about motherhood and childcare in relation to women's psychological health. The current study was designed to explore intensive mothering ideology changes after childbirth in primiparous and multiparous women, and the associations between these changes and maternal psychological health, specifically depression symptoms and burnout.

Intensive mothering ideology

According to Hays's seminal work (1996), the prevailing dominant discourse about motherhood should be regarded as an ideology that centers on three interconnected beliefs: mothers are the best caregivers for children; parenting is a difficult, all-consuming, childcentered and expert-guided activity, as well as the most important and fulfilling job; and children must be cherished because of their innocence and preciousness. In the same vein, according to [START_REF] Liss | Development and validation of a quantitative measure of intensive parenting attitudes[END_REF], intensive mothering ideology also incorporates the belief that mothers are better at parenting than fathers (essentialism); being a parent is rewarding (fulfilment); child-rearing is difficult (challenge); children must be intellectually stimulated (stimulation); and child-rearing should be focused on the child's individual needs and rhythms (child-centrism).

The intensive mothering ideology concept, although it originated in the United States, has been successfully applied to French mothers and mothers-to-be with some subtle adjustments, presumably because of cultural and social variation [START_REF] Loyal | Validity of the Measure of Intensive Mothering Ideology (MIMI)[END_REF][START_REF] Loyal | Intensive mothering ideology in France: A pilot study[END_REF]. Indeed, American and French women share some ideas about childcare and motherhood, but they may also exhibit differences [START_REF] Bornstein | Cultural Approaches to Parenting[END_REF][START_REF] Suizzo | French and European American child-mother play: Culture and gender considerations[END_REF]. For instance, compared to American mothers, French women have been found to place less value on bonding, breastfeeding, sacrificing their own needs and responding quickly to those of the baby, and to place more value on equal task-sharing between parents and child autonomy [START_REF] Suizzo | French and American Mothers' Childrearing Beliefs: Stimulating, Responding, and Long-Term Goals[END_REF]. Moreover, the United States and France have very different child and family policies [START_REF] Thevenon | Family policies in OECD countries: A comparative analysis[END_REF]. Unlike American parents, French parents benefit from childcare provisions, paid parental leave and family allowances [START_REF] Thevenon | Family Policies: France[END_REF].

It has been shown that intensive mothering ideology is more endorsed by mothers than by childless women [START_REF] Liss | Development and validation of a quantitative measure of intensive parenting attitudes[END_REF][START_REF] Loyal | Validity of the Measure of Intensive Mothering Ideology (MIMI)[END_REF]. This may be because women who endorse intensive mothering ideology may be more likely to start a family (self-selection bias). In addition, women giving birth may experience a growth in intensive mothering ideology as a part of their role transition (role transition effect). It has been observed that after the birth of a child, mother's gender role attitudes become more traditional [START_REF] Baxter | A Life-Changing Event: First Births and Men's and Women's Attitudes to Mothering and Gender Divisions of Labor[END_REF][START_REF] Corrigall | Gender Role Attitudes and Careers: A Longitudinal Study[END_REF][START_REF] Evertsson | The importance of work: Changing work commitment following the transition to motherhood[END_REF][START_REF] Katz-Wise | Gender-role attitudes and behavior across the transition to parenthood[END_REF][START_REF] Regnier Loilier | L'arrivée d'un enfant modifie-t-elle la répartition des tâches domestiques au sein du couple ?[END_REF]. In the same vein, one can reasonably expect that during the transition to motherhood, women may exhibit various changes regarding their ideas about motherhood and children such as intensive mothering ideology. One longitudinal study found that intensive mothering ideology did not increase between 4 and 16 months postpartum [START_REF] Walls | Intensive Mothering Beliefs Among Full-Time Employed Mothers of Infants[END_REF]. However, no longitudinal studies have been conducted regarding changes in intensive mothering ideology after the birth of a child.

It is often assumed that primiparous mothers face greater and more numerous changes than multiparous women when having a child because they are experiencing an entirely new role [START_REF] Dipietro | Continuity in self-report measures of maternal anxiety, stress, and depressive symptoms from pregnancy through two years postpartum[END_REF]. Indeed, it has been observed that after the birth of a child, primiparous mothers experience greater changes in gender role attitudes than multiparous mothers [START_REF] Baxter | A Life-Changing Event: First Births and Men's and Women's Attitudes to Mothering and Gender Divisions of Labor[END_REF][START_REF] Katz-Wise | Gender-role attitudes and behavior across the transition to parenthood[END_REF]. Presumably, primiparous mothers might also exhibit stronger changes regarding their ideas about motherhood and children, such as intensive mothering ideology.

Postpartum Depression and Maternal Burnout

There is no doubt that blissful motherhood is a collective aspiration, but it is well established that many women experience distress after the birth of a child (World Health Organization [START_REF] Who | Mental Health Aspects of Women's Reproductive Health: A Global Review of the Literature[END_REF]. The literature about mental health during the perinatal period is dominated by discussions of postpartum depression [START_REF] O'hara | Postpartum depression: Current status and future directions[END_REF][START_REF] Rallis | The transition to motherhood: Towards a broader understanding of perinatal distress[END_REF][START_REF] Who | Mental Health Aspects of Women's Reproductive Health: A Global Review of the Literature[END_REF], which is prevalent in 13-19% of women giving birth [START_REF] O'hara | Postpartum depression: Current status and future directions[END_REF]. Postpartum depression is associated with stigma [START_REF] Mcloughlin | Stigma associated with postnatal depression: A literature review[END_REF] and may have important consequences for children [START_REF] O'hara | Postpartum depression: Current status and future directions[END_REF][START_REF] Who | Mental Health Aspects of Women's Reproductive Health: A Global Review of the Literature[END_REF], such as psychopathological disorders [START_REF] Goodman | Maternal Depression and Child Psychopathology: A Meta-Analytic Review[END_REF], impaired cognitive development [START_REF] Kingston | Prenatal and Postpartum Maternal Psychological Distress and Infant Development: A Systematic Review[END_REF], and insecure attachment [START_REF] Misri | Perinatal Depression, Fetal Bonding, and Mother-Child Attachment: A Review of the Literature[END_REF]. Some scholars have also started to explore psychological distress in parents by looking at it from the perspective of burnout [START_REF] Mikolajczak | Consequences of parental burnout: Its specific effect on child neglect and violence[END_REF][START_REF] Mikolajczak | Exhausted Parents: Sociodemographic, Child-Related, Parent-Related, Parenting and Family-Functioning Correlates of Parental Burnout[END_REF][START_REF] Roskam | Exhausted Parents: Development and Preliminary Validation of the Parental Burnout Inventory[END_REF]. Whereas burnout was originally thought to be limited to job-related stress, and chiefly to healthcare, social, and teaching occupations [START_REF] Schaufeli | Burnout: 35 years of research and practice[END_REF], some scholars are now applying the concept to non-professional activities (e.g., postgraduate education, sports, parenting; [START_REF] Bianchi | Is burnout solely jobrelated? A critical comment[END_REF]. According to [START_REF] Roskam | Exhausted Parents: Development and Preliminary Validation of the Parental Burnout Inventory[END_REF], parental burnout encompasses three dimensions: exhaustion (extreme physical and emotional tiredness in the parental role), emotional distancing (diminished involvement in childcare), and feelings of incompetence as a parent. Those dimensions to some extent mirror the original occupational burnout dimensions [START_REF] Schaufeli | Burnout: 35 years of research and practice[END_REF]. Parental burnout may have serious consequences such as conjugal conflict or neglect and violence against children [START_REF] Mikolajczak | Consequences of parental burnout: Its specific effect on child neglect and violence[END_REF]. It may affect up to 13% of parents [START_REF] Roskam | Exhausted Parents: Development and Preliminary Validation of the Parental Burnout Inventory[END_REF], although it is difficult to establish cut-off and prevalence values regarding burnout [START_REF] Brisson | Stranger Things: On the Upside Down World of Burnout Research[END_REF].

According to attachment theory, women's deep involvement in mothering supports maternal satisfaction and competence as well as child development [START_REF] Bowlby | Maternal care and mental health[END_REF][START_REF] Bowlby | Attachment and Loss[END_REF].

Nevertheless, according to some scholars, normative aspects of motherhood could be significant contributors to distress in mothers [START_REF] Arendell | Conceiving and investigating motherhood: The decade's scholarship[END_REF][START_REF] Beck | Postpartum depression: A metasynthesis[END_REF][START_REF] Mcloughlin | Stigma associated with postnatal depression: A literature review[END_REF][START_REF] Patel | An exploration of illness beliefs in mothers with postnatal depression[END_REF][START_REF] Tummala-Narra | Contemporary impingements on mothering[END_REF]. Indeed, [START_REF] Rizzo | Insight into the parenthood paradox: Mental health outcomes of intensive mothering[END_REF] observed that in mothers of toddlers, essentialism and challenge were associated with lower life satisfaction and more symptoms of depression and stress while controlling for social support. In addition, [START_REF] Meeussen | Feeling Pressure to Be a Perfect Mother Relates to Parental Burnout and Career Ambitions[END_REF] found that intensive mothering ideology was associated with higher parental burnout through maternal gatekeeping behavior. However, [START_REF] Walls | Implications of Intensive Mothering Beliefs for the Well-Being of Full-Time Employed Mothers of Infants: Moderating Effects of Childcare Satisfaction and Workplace Flexibility[END_REF] found no association between intensive mothering ideology assessed at four months postpartum and maternal wellbeing at 16 months postpartum. Finally, [START_REF] Henderson | The Price Mothers Pay, Even When They Are Not Buying It: Mental Health Consequences of Idealized Motherhood[END_REF] found that intensive mothering ideology was not associated with maternal self-efficacy, stress or anxiety. However, pressure to be perfect and guilt for not meeting expectations were associated with maternal self-efficacy, stress or anxiety. However, those studies had various limitations. Most of them were cross-sectional [START_REF] Henderson | The Price Mothers Pay, Even When They Are Not Buying It: Mental Health Consequences of Idealized Motherhood[END_REF][START_REF] Meeussen | Feeling Pressure to Be a Perfect Mother Relates to Parental Burnout and Career Ambitions[END_REF][START_REF] Rizzo | Insight into the parenthood paradox: Mental health outcomes of intensive mothering[END_REF] or failed to use validated tools to assess intensive mothering ideology [START_REF] Henderson | The Price Mothers Pay, Even When They Are Not Buying It: Mental Health Consequences of Idealized Motherhood[END_REF][START_REF] Meeussen | Feeling Pressure to Be a Perfect Mother Relates to Parental Burnout and Career Ambitions[END_REF][START_REF] Walls | Implications of Intensive Mothering Beliefs for the Well-Being of Full-Time Employed Mothers of Infants: Moderating Effects of Childcare Satisfaction and Workplace Flexibility[END_REF]. Only Walls's study (2010) was longitudinal, and only Rizzo et al.'s study (2013) used the Intensive Parenting Attitude Questionnaire (IPAQ).

Aim of the Current Study

The current study was designed to explore intensive mothering ideology changes after childbirth in primiparous and multiparous women and the associations between these changes and maternal psychological health (depression symptoms and burnout). It was hypothesized that endorsement of intensive mothering ideology would be stronger after childbirth (H1).

intensive mothering ideology changes were expected to be stronger in primiparous mothers than in multiparous mothers (H2). Growth in intensive mothering ideology was expected to be associated with lower maternal psychological health (i.e., more depression symptoms and burnout) (H3).

Method

Participants and Procedure

Participants were expectant women who were followed up after childbirth. They had to be fluent in French (spoken and written) and older than 18. Women with multiple pregnancies or who had undergone medically assisted procreation, which might be a source of medical complications and emotional distress, were excluded [START_REF] Blondel | Les naissances en 2010 et leur évolution en 2003[END_REF][START_REF] Choi | Multiple Births Are a Risk Factor for Postpartum Maternal Depressive Symptoms[END_REF][START_REF] Hammarberg | Psychological and social aspects of pregnancy, childbirth and early parenting after assisted conception: A systematic review[END_REF]. The participants were recruited at the maternity ward of a local French university hospital during a required informational meeting about childbirth pain management. Approximately 640-960 women were invited to participate, and 144 were recruited (a participation rate of around 15-23%). Women who chose not to participate may have done so because they did not meet the inclusion/exclusion criteria or because they did not wish to participate.

Before the birth (T1), participants (n = 144) were received individually in a quiet office of the maternity ward. They were given information regarding the study, signed an informed consent form and completed a set of self-administered questionnaires. Then, two months (T2) and four months (T3) after the birth, they were asked to answer various selfadministrated questionnaires online. Between T1 (n = 144) and T2 (n = 138), six participants were lost (4.2%). Between T2 (n = 138) and T3 (n = 129), nine participants were lost (6.5%).

Informed consent was obtained from all individual participants included in the study.

All procedures were in accordance with the ethical standards of the institutional and national research committees and with the 1964 Declaration of Helsinki and its later amendments. The study was reviewed and approved by an institutional review board prior to data collection.

Measures

Intensive Mothering Ideology

The Mesure de l'Ideologie du Maternage Intensif (MIMI) was administered [START_REF] Loyal | Intensive mothering ideology in France: A pilot study[END_REF] at T1, T2 and T3. This French scale contains both translated items from the Intensive Parenting Attitude Questionnaire (IPAQ) [START_REF] Liss | Development and validation of a quantitative measure of intensive parenting attitudes[END_REF] and items derived from semi-structured interviews with French mothers and mothers-to-be [START_REF] Loyal | Intensive mothering ideology in France: A pilot study[END_REF]. The MIMI contains 21 items assessing six dimensions of intensive mothering ideology: essentialism expresses the idea that mothers are the best caregivers for children (seven items); consuming fulfillment expresses the idea that being a parent is a fulfilling, rewarding and allconsuming role (five items); child-centrism conveys the idea that child-rearing should be focused on the child's individual needs and rhythms (two items); challenge expresses the idea that child-rearing is the hardest job in the world (two items); sacrifice conveys the idea that parents should set aside their own desires (three items); and stimulation expresses the idea that children should be properly stimulated (two items). Participants were asked to answer each item on a Likert scale ranging from 1 (disagree very strongly) to 6 (agree very strongly).

Score for each dimension was calculated (mean). Higher score indicate a higher endorsement of the intensive mothering belief. The full scale is available in the original validation study [START_REF] Loyal | Intensive mothering ideology in France: A pilot study[END_REF]. The distinction between challenge and sacrifice did not appear explicitly in the pioneering conceptualization of intensive mothering ideology [START_REF] Hays | The cultural contradictions of motherhood[END_REF] or in the IPAQ [START_REF] Liss | Development and validation of a quantitative measure of intensive parenting attitudes[END_REF], but was observed in the MIMI development process [START_REF] Loyal | Intensive mothering ideology in France: A pilot study[END_REF].

In the present sample, Cronbach alphas were computed for each dimension at T1, T2, and T3, respectively: essentialism (α = .74, .81, .80), consuming fulfillment (α = .63, .68, .67), child-centrism (α = .77, .86, .80), challenge (α = .57, .70, .83), sacrifice (α = .51, .59, .72) and stimulation (α = .37, .53, .59). Those alpha values are in accordance with those obtained in the validation study with mothers and mothers-to-be indicating a lower reliability of the challenge (.61), sacrifice (.61) and stimulation (.64) dimensions [START_REF] Loyal | Intensive mothering ideology in France: A pilot study[END_REF]. Cronbach alphas depend heavily on the number of items [START_REF] Lance | The Sources of Four Commonly Reported Cutoff Criteria: What Did They Really Say?[END_REF][START_REF] Streiner | Starting at the Beginning: An Introduction to Coefficient Alpha and Internal Consistency[END_REF]. Thus, we have computed mean interitem correlations, a better way to assess internal consistency [START_REF] Clark | Constructing validity: Basic issues in objective scale development[END_REF]. Inter-item correlations were computed for essentialism (.27-.37), consuming fulfillment (.25-.32), child-centrism (.61-.74), challenge (.46-.73), sacrifice (.29-.43) and stimulation (.31-.44). As recommended by [START_REF] Clark | Constructing validity: Basic issues in objective scale development[END_REF], all mean interitem correlations are higher than .15 (also >.40 indicates a narrower construct). Of note, the Brown-Spearman prophecy formula indicates that increasing the number of items for fulfilment (adding three items), challenge (two items) sacrifice (two items), and stimulation (one item) might increase the Cronbach alphas to adequate levels (>.70). However, the MIMI has previously shown good criterion validity through its significant association with motherhood, housewifery and education [START_REF] Loyal | Validity of the Measure of Intensive Mothering Ideology (MIMI)[END_REF].

Depressive Symptoms

To assess depressive symptoms, the French version of the Edinburgh Postnatal Depression Scale (EPDS; [START_REF] Cox | Detection of postnatal depression: Development of the 10-item Edinburgh Postnatal Depression Scale[END_REF][START_REF] Guedeney | Validation study of the French version of the Edinburgh Postnatal Depression Scale (EPDS): New results about use and psychometric properties[END_REF]) was administered at T1, T2 and T3. This scale contains 10 items with four possible responses (0-3). Each item has different response options. The EPDS Score is the total of the scale (from 0 to 30).

Higher scores indicate higher depressive symptoms. This scale was chosen because it has been widely used and validated with new mothers and, to a lesser extent, pregnant women [START_REF] Gibson | A systematic review of studies validating the Edinburgh Postnatal Depression Scale in antepartum and postpartum women[END_REF]. Internal consistencies were satisfactory at T1, T2 and T3 (α = 0.83, 0.86, and 0.80, respectively).

Maternal Burnout

To assess burnout, two instruments were used during the postnatal period (T2 and T3) but not during pregnancy (T1) because burnout associated with parenting was the area of concern. First, the French translation of the Shirom Melamed Burnout Measure (SMBM) was administrated [START_REF] Sassi | Translation and validation of a new measurement of professional exhaustion: The Shirom-Melamed Burnout Measure[END_REF][START_REF] Shirom | A Comparison of the Construct Validity of Two Burnout Measures in Two Groups of Professionals[END_REF]. The SMBM is a 14-item scale assessing physical exhaustion (six items), cognitive exhaustion (five items), emotional exhaustion (three items) and global exhaustion (all items). Each item was offered with a Likert scale ranging from 1 (never) to 7 (always). A few modifications were made to adapt the scale to mothers, for instance, the emotional exhaustion items: "I feel I am unable to be sensitive to the needs of my child." Scores are computed for each dimension (mean). Higher scores indicate more symptoms of burnout. Exploratory factor analyses (principal factor analysis and oblimin rotation) were conducted. The structure of the scale was the same as expected, and internal consistencies were satisfactory for physical, cognitive, emotional and global exhaustion at T2 (α = .91, .96, .78 and .92, respectively) and T3 (α = .93, .95, .85 and .93, respectively).

Second, the Questionnaire d'Auto-Evaluation de la Compétence Educative Parentale (QAECEP; [START_REF] Terrisse | Le questionnaire d'autoevaluation de la comptetence educative parentale (QAECEP). Groupe de recherche en adaptation scolaire et sociale[END_REF] was used. This scale is the French adaptation of the Parental Sense of Competence Scale (PSOC; [START_REF] Gibaud-Wallston | Development and utility of the Parenting Sense of Competence Scale[END_REF][START_REF] Johnston | A measure of parenting satisfaction and efficacy[END_REF]. The QAECEP was used because a sense of incompetence is one of the three components of burnout [START_REF] Roskam | Exhausted Parents: Development and Preliminary Validation of the Parental Burnout Inventory[END_REF] that is not assessed by the SMBM. The QAECEP is a 16-item scale offered with a Likert scale ranging from 1 (strongly agree) to 6 (strongly disagree). Scores are computed for each dimension (mean). Higher scores indicate more competence and satisfaction. Exploratory factor analyses (principal factor analysis, oblimin rotation) were conducted. The structure of the scale was quite different from the original one. Six items (items 3, 4, 8, 9, 13 and 16) were loading on the satisfaction dimension ("Although I've only been a mother for a short time, I feel comfortable in this role"). Five items (items 1, 6, 7, 10 and 11) were loading on the competence dimension ("A new mother could learn to be a good mother by following my example"). Finally, two items (items 12 and 14) were combined in an unexpected interest dimension ("If being a mother of a young child was more interesting, I would be more motivated to play my role as a mother"). Items 2, 5 and 15 were dropped because of low loadings. Internal consistencies were computed for satisfaction, competence and interest at T2 (α = .81, .65 and .65, respectively) and T3 (α = .78, .72 and .76, respectively). The different factor structure means that our results should not be compared directly to previous ones using the original factor structure.

Data Analyses

Analyses were performed with R Software (https://www.r-project.org/). First, participants who were lost during the follow-ups (n = 15) were compared to the others (n = 129) with a Fisher exact test and mean comparisons. Then a two-way mixed MANOVA (Multivariate analysis of variance) was computed including time (within subjects, three levels: T1, T2 and T3) and parity (between subjects, two levels: primiparous and multiparous women). When needed, post-hoc comparisons (with Bonferroni correction) were computed to check for significant differences. Second, linear mixed models were computed (https://cran.rproject.org/package=lcmm) to test various models predicting changes in depression symptoms and burnout according to changes in intensive mothering ideology. Linear mixed models are specifically designed for the analysis of longitudinal data [START_REF] Laird | Random-effects models for longitudinal data[END_REF]. This approach offers the advantage of considering multiple observations within a subject, taking intrasubject correlations into account. It also enables adjustments for numerous potential confounding variables. All models were controlled for parity (primiparous vs multiparous women) and unemployment. Models predicting changes in burnout were controlled for changes in depressive symptoms.

Results

Descriptive Statistics

Participants' characteristics are described in Table 1. The Fisher exact test demonstrated that women who did not complete the whole protocol (n = 15) were more likely to have had an unplanned pregnancy (53% vs 12%, p < .05). They were more often born abroad (20% vs 5%, p < .05) and had a lower level of education (53% vs 26%, p < .05). They also had lower essentialism (t(142) = 2.77, p < .01), and sacrifice (t(142) = 2.09, p < .05) scores.

INSERT TABLE 1

Changes in Intensive Mothering Ideology (H1)

First, as expected, intensive mothering ideology (with the exceptions of essentialism and stimulation) grew stronger (Table 2). Thus, our first hypothesis (H1) regarding growth in intensive mothering ideology was mostly confirmed. Differences were significant only from T1 (pregnancy) to T2 or T3 (two or four months after childbirth), suggesting somewhat early changes.

INSERT TABLES 2 AND 3

Changes in Mothering Ideology According to Parity (H2)

No interaction was observed between time and parity (Table 2), indicating that primiparous women did not exhibit higher changes in intensive mothering ideology compared to multiparous women. Our second hypothesis (H2) was not confirmed. However, challenge and sacrifice scores were higher in multiparous women than in primiparous women (Tables 2 and3).

Changes in Mothering Ideology and Maternal Psychological Health (H3)

Changes in intensive mothering ideology were associated with changes in depression and burnout symptoms (Table 4). Mainly, increases in sacrifice ideas were associated with more depression as well as more physical, cognitive, emotional and global exhaustion. (β = .13, .37, .26, .28 and .36) and lower parental satisfaction, competence and interest (β = -.41, -.20 and -.17). Increases in challenge were associated with more physical exhaustion (β = .18) but also with more interest in the parental role (β = .17). Essentialism was associated with more depression (β = .13) but also with more satisfaction and competence in the parental role (β = .20 and .22) and less emotional exhaustion (β = -.20). Increases in other dimensions of intensive mothering ideology seem to be generally positive. Increases in consuming fulfillment were associated with more satisfaction, competence and interest in the parental role (β = .27, .20 and .66). Increases in child-centrism were associated with more satisfaction and competence in the parental role (β = .17 and .16). Finally, increases in stimulation were associated with less emotional exhaustion (β = -.59). Our last hypothesis (H3) was only partly confirmed. Only increased sacrifice seemed to have clearly deleterious effects.

INSERT TABLE 4

Discussion

Our results show that most dimensions of intensive mothering ideology increased after the birth of a child. However, this increase in intensive mothering ideology was not higher in primiparous women compared to multiparous women. Of note, the challenge and sacrifice dimensions were higher in multiparous women than in primiparous women. In addition, sacrifice was the only dimension for which increases were consistently associated with more symptoms of depression and burnout.

Past research has shown that intensive mothering ideology is endorsed more strongly by mothers than by childless women [START_REF] Liss | Development and validation of a quantitative measure of intensive parenting attitudes[END_REF][START_REF] Loyal | Validity of the Measure of Intensive Mothering Ideology (MIMI)[END_REF]. This effect might be partly explained by a self-selection bias because women who endorse intensive mothering ideology more strongly may also be more likely to start families. However, our results suggest that this effect might also be explained by changes occurring after the birth of a child (role transition effect). In sum, after the birth of a child, women are more convinced that childcare is a consuming and fulfilling activity, that it is a challenge that requires many sacrifices, and that it should be organized according to a child's needs and rhythms. Thus, our first hypothesis was confirmed. Becoming a mother is a role transition accompanied by changes in values and beliefs. To our knowledge, this is the first longitudinal study to bring to light intensive mothering ideology changes associated with the birth of a child. As with gender ideology [START_REF] Corrigall | Gender Role Attitudes and Careers: A Longitudinal Study[END_REF], intensive mothering ideology is not a strictly fixed property of individuals but rather may evolve to accommodate reproductive and family life stages. Interestingly, changes were mainly observed between pregnancy (T1) and two or four months after childbirth (T2 or T3), but not between two months (T2) and four months after childbirth (T3). Thus, intensive mothering ideology growth may occur early after childbirth (role attainment effect) but not thereafter (role practice effect). However, our sample was mostly composed of highly educated women with skilled jobs who had resumed their professional activity at four months after childbirth (see Table 1). Continuous changes could occur in women who do not resume their professional activities.

Only essentialism and stimulation beliefs did not increase after childbirth. This outcome is consistent with previous findings that demonstrated stimulation beliefs were not higher in French mothers than in childless women [START_REF] Loyal | Validity of the Measure of Intensive Mothering Ideology (MIMI)[END_REF]. However, it has been previously observed that essentialism is stronger in mothers than in childless women (Liss et al., 2013;[START_REF] Loyal | Validity of the Measure of Intensive Mothering Ideology (MIMI)[END_REF]. Growth in essentialism beliefs might occur earlier during pregnancy, or even during pregnancy planning, or later when new mothers have endured months of conflicting work and family demands and unbalanced division of parental and domestic duties [START_REF] Regnier Loilier | L'arrivée d'un enfant modifie-t-elle la répartition des tâches domestiques au sein du couple ?[END_REF].

Inconsistent with our hypothesis, primiparous women did not exhibit stronger changes in intensive mothering ideology than multiparous women. This result is at odds with various studies showing that after the birth of a child, primiparous mothers experience greater changes in gender role attitudes than multiparous mothers [START_REF] Baxter | A Life-Changing Event: First Births and Men's and Women's Attitudes to Mothering and Gender Divisions of Labor[END_REF][START_REF] Katz-Wise | Gender-role attitudes and behavior across the transition to parenthood[END_REF].

However, the women in our sample were first assessed only one month before giving birth (Table 1). It may be possible to observe greater changes in primiparous women earlier in the pregnancy, or even during pregnancy planning.

Regarding the effects of intensive mothering ideology changes on symptoms of depression and burnout, the results showed mixed effects. Thus, considering intensive mothering ideology as a whole to be detrimental to maternal psychological health may not provide much insight into its effects. In fact, different intensive mothering ideology components might produce different effects.

First, growth in consuming fulfillment, child-centrism and stimulation had positive effects. Women who are consumed by a fulfilling and child-centered parental role requiring child-stimulating activities experience more satisfaction, feelings of competence, interest in the parental role and connectedness with their child. This is in accordance with canonical theories suggesting that a mother's personal investment in motherhood promotes maternal psychological health [START_REF] Bowlby | Maternal care and mental health[END_REF][START_REF] Bowlby | Attachment and Loss[END_REF]. Supporting positive, sensitive and stimulating interactions between the mother and the child is known to be of paramount importance when dealing with depressed mothers [START_REF] Milgrom | Dépistage et traitement de la dépression postnatale (DPN)[END_REF].

Second, growth in essentialism and challenge was associated with paradoxical effects.

Believing that childcare is difficult women's work promotes feelings of satisfaction, competence, interest and connectedness but is also a source of depression as well as physical and general exhaustion. Construing childcare as a difficult activity that rests on the mother's shoulders might help in building mothering identity, role meaning and pride [START_REF] Nelson | The pains and pleasures of parenting: When, why, and how is parenthood associated with more or less well-being?[END_REF], but it might also increase exhaustion and depression because of higher perceived costs [START_REF] Who | Mental Health Aspects of Women's Reproductive Health: A Global Review of the Literature[END_REF]. Of note, essentialist beliefs may be a source of partner under-involvement in childcare through a possible association with gatekeeping, a collection of behaviors that inhibit partner involvement [START_REF] Meeussen | Feeling Pressure to Be a Perfect Mother Relates to Parental Burnout and Career Ambitions[END_REF]. Indeed, lack of conjugal support is a well-known source of distress in new mothers [START_REF] O'hara | Postpartum depression: Current status and future directions[END_REF], but instrumental support provided by the partner might also decrease the mother's feelings of self-efficacy [START_REF] Sasaki | The supermom trap: Do involved dads erode moms' self-competence?[END_REF]. The role of unmet expectations regarding partner support might also be an important variable, as it is known to produce distress [START_REF] Biehle | First-time parents' expectations about the division of childcare and play[END_REF][START_REF] Goldberg | Division of Labor and Working-Class Women's Well-Being Across the Transition to Parenthood[END_REF][START_REF] Gremigni | Partner support and postpartum depressive symptoms[END_REF][START_REF] Khazan | Violated wishes about division of childcare labor predict early coparenting process during stressful and nonstressful family evaluations[END_REF].

Finally, women who felt that parenthood requires sacrifice felt less competent, satisfied and interested in their role, as well as more depressed and exhausted physically, cognitively, emotionally and globally. This outcome is in accordance with the suggestions of various scholars that some normative aspects of motherhood could contribute to distress in new mothers [START_REF] Beck | Postpartum depression: A metasynthesis[END_REF][START_REF] Mcloughlin | Stigma associated with postnatal depression: A literature review[END_REF][START_REF] Patel | An exploration of illness beliefs in mothers with postnatal depression[END_REF][START_REF] Tummala-Narra | Contemporary impingements on mothering[END_REF]. Those results could be specific to French women. Indeed, previous studies have shown that, compared to American women, French women place less value on bonding, breastfeeding and sacrificing their own needs while responding quickly to those of the baby, and more value on equal task-sharing between parents and child autonomy [START_REF] Suizzo | French and American Mothers' Childrearing Beliefs: Stimulating, Responding, and Long-Term Goals[END_REF]. Beliefs about sacrifice might conflict strongly with French women's desire for independence and workfamily life balance. Moreover, sacrifice beliefs could be similar to "self-silencing," or women's restrictions on their self-expression within their relationships to meet the needs of others [START_REF] Boughton | Integrated review of the social and psychological gender differences in depression[END_REF][START_REF] Jack | Silencing The Self: Women and Depression[END_REF]. Our results reinforce the need for reduction of sacrificial beliefs and instead fostering self-care promotion goals directed at mothers-to-be and new mothers [START_REF] Cuijpers | Psychological treatment of postpartum depression: A meta-analysis[END_REF][START_REF] Leight | Treatment of post-partum depression: A review of clinical, psychological and pharmacological options[END_REF][START_REF] Milgrom | Dépistage et traitement de la dépression postnatale (DPN)[END_REF][START_REF] Sockol | A meta-analysis of treatments for perinatal depression[END_REF].

Of note, multiparous women had higher sacrifice and challenge scores than primiparous women. This finding might be explained by the fact that multiparous women are subjected to stronger family demands because they are raising older children [START_REF] Dipietro | Continuity in self-report measures of maternal anxiety, stress, and depressive symptoms from pregnancy through two years postpartum[END_REF][START_REF] Grant | Maternal anxiety during the transition to parenthood: A prospective study[END_REF]. This could explain why multiparous women are sometimes found to experience more distress after the birth of their child [START_REF] Bell | Childbirth and symptoms of postpartum depression and anxiety: A prospective birth cohort study[END_REF][START_REF] Grant | Maternal anxiety during the transition to parenthood: A prospective study[END_REF][START_REF] Milgrom | Antenatal risk factors for postnatal depression: A large prospective study[END_REF][START_REF] Yelland | Postpartum anxiety, depression and social health: Findings from a population-based survey of Australian women[END_REF].

Limitations and Future Research

This study also has some limitations. First, there is now a specific and well-validated scale (Parental Burnout Inventory; [START_REF] Roskam | Exhausted Parents: Development and Preliminary Validation of the Parental Burnout Inventory[END_REF] designed to measure parental burnout. This scale was not yet available when this study was conducted. Measuring parental burnout with specific rather than generic tools not directed at parents (the SBMB) could have provided more accurate results. Second, changes in intensive mothering ideology were modest in magnitude (≤.10) [START_REF] Sullivan | Using Effect Size-Or Why the P Value Is Not Enough[END_REF]. This might be explained by our sample, which was mostly composed of highly educated women engaged in skilled occupations (see Table 1). This is a quite common limitation in perinatal research [START_REF] Ross | Demographic characteristics of participants in studies of risk factors, prevention, and treatment of postpartum depression (English)[END_REF].

According to [START_REF] Bloss | Introduction[END_REF], mother identity may be more strongly endorsed in poorly educated new mothers with precarious and less-skilled jobs. Thus, studying intensive mothering ideology changes in disadvantaged populations could be a promising research avenue. Third, participants were followed up only from late pregnancy to two and four months after childbirth. This narrow follow-up period prevented us from catching early changes that could have occurred since the planning of the pregnancy and late changes that could have occurred after months of conflicting family and work demands and unequal distribution of domestic and parental chores between spouses. For instance, it would be interesting to study how changes in intensive mothering ideology might be associated with professional issues when women return to work. Thus, further research should explore how intensive mothering ideology could change over longer periods of family life and how it may influence familial and professional issues. Finally, this study does not include data regarding women who did not become mothers (control group). It is possible that women of childbearing age might also exhibit changes over time in intensive mothering ideology without having a child.

Practice Implications

Our results highlight a need for professionals working with expectant women and new mothers (physician, midwifes, social workers, etc.) to pay attention to changes in patients' ideas and beliefs about motherhood and mothering. Sacrifice beliefs, and to a lesser extent challenge and essentialism beliefs, could be monitored to reduce factors that were shown to be related to depression and burnout after a birth, especially in multiparous women. Such beliefs could be discussed during prenatal classes or addressed through flyers or short videos.

For instance, maternal gatekeeping behaviors [START_REF] Allen | Maternal Gatekeeping: Mothers' Beliefs and Behaviors That Inhibit Greater Father Involvement in Family Work[END_REF][START_REF] Fagan | The Relationship between Maternal Gatekeeping, Paternal Competence, Mothers' Attitudes about the Father Role, and Father Involvement[END_REF][START_REF] Gaunt | Biological Essentialism, Gender Ideologies, and Role Attitudes: What Determines Parents' Involvement in Child Care[END_REF][START_REF] Gaunt | Maternal Gatekeeping: Antecedents and Consequences[END_REF][START_REF] Mcbride | Paternal identity, maternal gatekeeping, and father involvement[END_REF][START_REF] Puhlman | Rethinking Maternal Gatekeeping: Rethinking Maternal Gatekeeping[END_REF] and preconceived ideas regarding the decisive and dominant role of mothers in childcare over fathers could be targeted, possibly through humor [START_REF] Riquelme | Subversive humor against sexism: Conceptualization and first evidence on its empirical nature[END_REF].

Family members could also be called upon to address those beliefs in everyday life.

New fathers could benefit from advice or interventions to assert firmly, at an early stage, their domestic and childcare skills and their rightful role with newborns [START_REF] Doherty | An intervention to increase father involvement and skills with infants during the transition to parenthood[END_REF].

They could also be trained to spot and counter, in a caring manner, sacrifice beliefs and maternal gatekeeping in their loved ones.

Conclusions

As expected, our results confirm that intensive mothering ideology grows stronger after childbirth. This is the first time that such changes are documented. Intensive mothering ideology is not a strictly fixed property of individuals but rather may evolve to accommodate reproductive and family life stages. This result call for further longitudinal research.

Moreover, some intensive mothering ideology dimensions (challenge and sacrifice) are higher in multiparous women than in primiparous women probably indicating a higher domestic and parental load in multiparous women. However, contrary to our hypothesis, intensive mothering ideology increases are presumably not stronger in primiparous women. Finally, the effects of intensive mothering ideology changes on symptoms of depression and burnout were mixed. Considering intensive mothering ideology as a whole to be detrimental to maternal psychological health may not provide much insight into its precise effects. However, growth in sacrificial beliefs clearly favors the development of mental health issues. It calls for interventions efforts to question our collective concept of motherhood. The tendency to sacrifice oneself is mostly understood as a positive and desirable feature especially in the motherhood context. Calling into question this motherly ideal will certainly be difficult but is a promising avenue.

Declarations

Funding. None.

Conflict of

  Interest. The authors declare that they have no competing interests. Research Involving Human Participants. All procedures were in accordance with the ethical standards of the institutional and national research committees and with the 1964 Declaration of Helsinki and its later amendments. Informed Consent. All participants in this work provided informed consent.

Table 1

 1 Participants Characteristics during Pregnancy(Time 1, N = 144)

	Variable	M (SD) or %
	Age (years)	30.9 (4.15)
	Born in France	93.75 %
	Engaged in a relationship	97.9%
	First time mother	72.9%
	Previous child	27.1%
	One child	84.6 %
	Youngest child age (months)	37.51 (18.86)
	Delay to Delivery	29.28 (13.24)
	≥ 3 years post-secondary Education	70.8 %
	Skill Level
	White collar / highly qualified	41.1 %
	Intermediate professional	39 %
	Employees	19.9 %
	Employed	80.6 %
	≥ 35 hours a week	90.5 %
	Pregnancy
	Planned	84%
	Happy to be pregnant	82.6%
	Obstetric complication
	Complicated or urgent C-section	8.7%
	Prematurity (>30 days)	0%
	Underweight (<2kg)	0%
	Incubator (>4 weeks)	0%

Table 2

 2 Two-Way Mixed MANOVA according to Time and Parity

		df	Mean Square F	Sig	Partial Eta² Post-hoc
	Time
	Essentialism	1.754	0.691	1.245	.287	.010
	Consuming Fulfillment	1.454	1.713	3.464	.048*	.027	T1<T2&T3
	Child-centrism	1.638	6.761	7.623	.001**	.058	T1<T2&T3
	Challenge	1.737	2.795	2.747	.074 †	.022	T1<T3
	Sacrifice	1.685	6.834	10.071	.000**	.075	T1<T2&T3
	Stimulation	1.750	0.035	0.207	.784	.002
	Parity
	Essentialism	1	0.414	0.395	.531	.003
	Consuming Fulfillment	1	0.960	1.277	.261	.010
	Child-centrism	1	0.177	0.110	.741	.001
	Challenge	1	8.575	4.749	.031*	.037	MP>PM
	Sacrifice	1	11.020	11.472	.001**	.085	MP>PM
	Stimulation	1	0.007	0.028	.867	.000
	Time x Parity
	Essentialism	1.754	0.259	0.467	.602	.004
	Consuming Fulfillment	1.454	0.868	1.756	.184	.014
	Child-centrism	1.638	1.492	1.682	.193	.013
	Challenge	1.737	0.190	0.187	.799	.002
	Sacrifice	1.685	0.106	0.157	.819	.001
	Stimulation	1.750	0.074	0.439	.618	.004
	Note. T1: Pregnancy; T2: 2 months after childbirth; T3: 4 months after childbirth; MP: Multiparous
	women; PM: Primiparous women. Post-hoc comparisons with Bonferroni corrections are significant
	at p<.05. p<.01 (**), p<.05 (*) or p<.10 ( †).

Table 3

 3 Descriptive Statistics regarding Intensive Mothering Ideology according to Time and Parity

		T1.	T2	T3
		M (SD)	M (SD)	M (SD)
	Essentialism	MP 3.20 (0.66)	MP. 3.29 (1.02)	MP. 3.44 (0.74)
		PM. 3.18 (0.66)	PM. 3.27 (0.83)	PM. 3.26 (0.95)
		All. 3.19 (0.66)	All.3.27 (0.88)	All. 3.30 (0.89)
	Consuming Fulfillment MP. 4.67 (0.76)	MP. 5.01 (0.67)	MP. 4.82 (0.70)
		PM. 4.87 (0.59)	PM. 4.95 (0.77)	PM. 5.03 (0.72)
		All. 4.81 (0.64)	All. 4.97 (0.75)	All. 4.97 (0.71)
	Child-centrism	MP. 4.11 (0.97)	MP. 4.71 (1.06)	MP. 4.51 (0.91)
		PM. 4.19 (0.98)	PM. 4.41 (1.10)	PM. 4.59 (0.98)
		All. 4.17 (0.97)	All. 4.50 (1.09)	All. 4.57 (0.96)
	Challenge	MP. 4.74 (1.13)	MP. 5.01 (0.90)	MP. 4.90 (1.20)
		PM. 4.34 (1.01)	PM. 4.65 (1.08)	PM. 4.65 (1.19)
		All. 4.45 (1.05)	All. 4.75 (1.04)	All. 4.72 (1.19)
	Sacrifice	MP. 3.02 (0.67)	MP. 3.33 (0.97)	MP. 3.55 (0.76)
		PM. 2.70 (0.76)	PM. 2.94 (0.82)	PM. 3.12 (0.95)
		All. 2.79 (0.75)	All. 3.04 (0.88)	All. 3.24 (0.92)
	Stimulation	MP. 5.74 (0.37)	MP. 5.73 (0.43)	MP. 5.73 (0.46)
		PM. 5.68 (0.46)	PM. 5.74 (0.45)	PM. 5.76 (0.40)
		All. 5.69 (0.43)	All. 5.73 (0.44)	All. 5.75 (0.42)
	Note. T1: Pregnancy; T2: 2 months after childbirth; T3: 4 months after childbirth; MP:
	Multiparous women; PM: Primiparous women; All: All participants.

Table 4 .

 4 Linear Mixed Models Predicting Changes in Symptoms of Depression and Burnout

		β	SE	Wald Sig
	Model 1. Depression
	Essentialism	.13	.07	1.78	.07 †
	Consuming Fulfillment	.04	.09	0.45	.65
	Child-centrism	-.09	.06	-1.37	.17
	Challenge	.01	.06	0.25	.80
	Sacrifice	.27	.08	3.60	.00**
	Stimulation	-.17	.13	-1.35	.18
	Model 2. Satisfaction
	Essentialism	.20	.09	2.06	.04*
	Consuming Fulfillment	.27	.12	2.25	.02*
	Child-centrism	.17	.10	1.78	.07 †
	Challenge	-.02	.08	-.0.25	.80
	Sacrifice	-.41	.10	-3.98	.00**
	Stimulation	-.02	.17	-0.10	.91
	Model 3. Competence
	Essentialism	.22	.08	2.55	.01*
	Consuming Fulfillment	.20	.11	1.80	.07 †
	Child-centrism	.16	.09	1.86	.06 †
	Challenge	.01	.07	0.11	.91
	Sacrifice	-.20	.09	-2.19	.03*
	Stimulation	.18	.16	1.17	.24
	Model 4. Interest.
	Essentialism	.12	.08	1.41	.16
	Consuming Fulfillment	.26	.11	2.35	.02*
	Child-centrism	.13	.08	1.52	.13
	Challenge	.17	.07	2.42	.02*
	Sacrifice	-.17	.09	-1.89	.06 †
	Stimulation	.10	.16	0.62	.54

Model 8. Global Ex.

  In each model, parity and unemployment are controlled. Depressive symptoms changes are controlled in all models expecting Model 1. p<.01 (**), p<.05 (*) or p<.10 ( †).

	Essentialism	-.05	.08	-0.61	.54
	Consuming Fulfillment	-.08	.11	-0.72	.47
	Child-centrism	-.02	.08	-0.19	.85
	Challenge	.16	.07	2.25	.02*
	Sacrifice	.36	.09	3.96	.00**
	Stimulation	-.07	.16	-0.48	.63
	Note.