Marie Thiollet-Scholtus
email: marie.thiollet-scholtus@inrae.fr

A Muller

C Abidon

J Grignion

O Keichinger

R Koller

A Langenfeld

L Ley

N Nassr

C Rabolin-Meinrad

J Wohlfahrt

Multidimensional assessment

Keywords: grapevine, multi-performance, evaluation, pesticide reduction, long-term Graphical

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Introduction

Grapevine (Vitis vinifera L.) is the topmost cash crop worldwide, being cultivated on 7.5 million hectares in 2015 [START_REF] Oiv | Distribution variétale du vignoble dans le monde[END_REF], producing nearly 74 million tons of fruit per year (FAOSTAT, 2017).

However, grapevine production has many negative environmental effects, mainly due to pesticide impacts on water quality [START_REF] Fiener | Managing erosion and water quality in agricultural watersheds by small detention ponds[END_REF], air quality [START_REF] Otto | Droplets deposition pattern from a prototype of a fixed spraying system in a sloping vineyard[END_REF], soil quality [START_REF] Klik | Soil conservation and crop productivity in austrian vineyards[END_REF] and biodiversity [START_REF] Thomson | Beneficial organisms as bioindicators for environmental sustainability in the grape industry in Australia[END_REF].

It is important to reduce these negative impacts while maintaining grape yield, grape quality, social sustainability, and profitability of the farms [START_REF] Dantsis | A methodological approach to assess and compare the sustainability level of agricultural plant production systems[END_REF][START_REF] Lichtfouse | Sustainable agriculture as a central science to solve global society issues[END_REF], while embracing the principles of sustainability. To address these issues, new low-input vine systems (NLIVS) that can achieve all these goals are required. NLIVS are co-conceived with winegrowers based on a range of agro-ecological principles and share the goal of reducing dependence on external inputs [START_REF] Wezel | The blurred boundaries of ecological, sustainable, and agroecological intensification: a review[END_REF]. NLIVS are thus diverse in their pesticide reduction levels and strategies. Pesticide reduction strategies in the assessed systems are based on the single or combined activation of three approaches: (i) technical (i.e., using essential oils to reduce copper use, 100% soil covering applied); (ii) organizational (i.e., new decision rules to spray, decision aid tools); and (iii) redesign of the entire system (resistant grape varieties planted). Once conceived, these NLIVS must be assessed (Pelzer et System assessm ent (25) Results al., 2012) in terms of all dimensions of sustainability. Moreover, their resilience, or temporal performance stability, must also be evaluated.

Multicriteria indicators

Pesticides

A recent research on the Web of Science with the keywords "vine" * "long term" * "experiment" (http://apps.webofknowledge.com/; accessed on 25 Nov. 2019) shows that very few (15) long-term sustainability assessments of viticulture systems have been reported. Most of them were performed at only one experimental site, and none performed broad multifactorial analysis to assess a diversity of systems [START_REF] Morlat | Long-term additions of organic amendments in a Loire valley vineyard. II. Effects on root system, growth, grape yield, and foliar nutrient status of a Cabernet franc vine[END_REF].

Multicriteria assessment methods for viticulture have been developed [START_REF] Pelzer | Assessing innovative cropping systems with DEXiPM, a qualitative multi-criteria assessment tool derived from DEXi[END_REF]. These methods can assess existing vine systems, including integrated and organic management, but do not accommodate new, very low-input approaches. Methods for use in such systems are needed. Existing assessments also consider few indicators simultaneously, such as those in which one quality and one life cycle assessment (LCA) indicator are calculated for each system [START_REF] Beauchet | Modeling the grape quality by multivariate analysis of viticulture practices, soil and climate[END_REF][START_REF] Beauchet | Lca Comparison Results With Midpoint Method Associated With Fuzzy Logic Vs[END_REF][START_REF] Fermaud | New multipest damage indicator to assess protection strategies in grapevine cropping systems[END_REF][START_REF] Merot | Hierarchical Patch Dynamics Perspective in Farming System Design[END_REF][START_REF] Thiollet-Scholtus | Using indicators to assess the environmental impacts of wine growing activity: the INDIGO® method[END_REF].

The main goal of this study was to assess the sustainability and performance of several new low-input viticulture systems over an extended period and a broad range of indicators. We assessed 11 new lowinput viticulture systems using 25 indicators over six years to provide generalizable knowledge about the impacts of these systems to enable potential adopters to evaluate them.

Material and methods

Case study

The 11 NLIVS case studies took place in Alsace, a wine region in north-eastern France (48°19'5.446"N, 7°26'29.847"E). Alsace is one of the top four French regions exporting white wines (FranceAgriMer, 2018). Grapes are the largest single French plant product in terms of value, at €11.2 billion of the €41.1 billion national total excluding subsidies [START_REF] Lubatti | L'agriculture en[END_REF]. Alsace has a temperate, maritime climate that is warm with moderate precipitation [START_REF] Blenkinsop | Developing climatic scenatios for pesticide fate modelling in Europe[END_REF]. Its climatic conditions combine moderate precipitation with temperatures influenced by oceanic air currents. This combination tends to reduce the survival of otherwise winter-resistant grapevine pathogens, and thus may be a favourable environment for experiments of very low pesticide use.

The 11 systems were studied over six years (2013)(2014)(2015)(2016)(2017)(2018). This extended period was essential to test the robustness and resilience of the studied systems to multiple pathogen pressures related to varying climatic conditions.

The 11 NLIVS cover a range of biophysical and agronomic conditions (Table 1), representing winegrowers' practices in the territory. Each of the participating winegrowers designed an NLIVS adapted to their objectives, constraints, and opportunities using or combining the three pesticidereduction methods described above. The NLIVS were labelled A to K, with A being the least different from conventional viticulture and K the vine system requiring the most structural and management changes (e.g. resistant vine variety). NLIVS A to E reduce pesticide use through technical changes, F to I through organizational changes and J and K through redesigning the entire system (Table 2).

Indicator data collection

Twenty-five quantitative sustainability indicators were calculated for each of the six growing seasons in each NLIVS. Results were converted into mean values across the studied years for each indicator.

They represented a broad spectrum of viticulture system sustainability dimensions, including agronomic criteria such as grape and wine quality, environmental, social, and economic elements (Table 3).

Indicators were calculated using data from two sources. First, information was collected during vineyard surveys undertaken annually, after each vine-growing season. This was used to calculate treatment frequency indexes (TFIs), I-Phy, copper usage rate, and socio-economic indicators (described below). These data included all the recorded management practices along with general information about the farm (number of hectares, number of workers, field size). Second, on-field measurements were taken several times over the years covering biodiversity indicators, soil compaction, bacterial activity and biomass in soil, damage caused by fungi, vine vigour and yield, and juice sugar and total acidity, depending on each indicator. All measurements and visual notations were made on ten groups of ten vines per NLIVS.

Environmental sustainability indicators

The pressure of plant protection products is assessed using the Treatment Frequency Index of each plot (TFIp) (OECD, 2001) :

with ARt the applied dose of product t, HRt the registered rate of product t; TAt the area of the plot treated with product t and PA, the plot area.

TFIp was calculated for all pesticide applications on each plot (TFI-total) and also for each pesticide category considered separately (TFI-total and TFI-fungicides).

We also calculated a TFI-biocontrol because substitution of chemical fungicide practices by biocontrol fungicide practices (i.e. using copper instead of folpel and sulphur instead of cyproconazol) is an important lever to reduce pesticide use in vine. While biocontrol fungicide practices are less harmful to the environment than chemical fungicide practices, they are nonetheless not harmless for some environmental compartments, such as soil accumulation of copper. TFI calculation for studied systems was compared to the local reference based on a 2013 national survey [START_REF] Pujol | Apports de produits phytosanitaires en viticulture et climat : une analyse à partir des enquêtes pratiques culturales[END_REF]. Reference values are 10.9 for TFI-total and 9.8 for TFI-fungicides. TFIbiocontrol reference is the TFI-biocontrol calculated for each studied system in 2013. Copper rate is the indicator that reports the level of copper used on each NLIVS. It is calculated as the amount of copper applied per hectare each year. Copper is an active ingredient for many biocontrol fungicides authorized in organic and biodynamic viticulture. Intensive use of copper might lead to soil pollution. Yearly copper rate is compared to the European authorized limit of 4 kg.ha -1 .year -1 and also to the local (i.e. northern France) practice reference of 1.5 kg.ha -1 .year -1 [START_REF] Pujol | Apports de produits phytosanitaires en viticulture et climat : une analyse à partir des enquêtes pratiques culturales[END_REF].

TFI measures only the reliance and dependence on pesticides. In addition to the TFIs, the environmental exposure to pesticides is assessed with the I-Phy indicator. This indicator assesses the pesticide exposure of groundwater, surface water, air, and beneficial organisms induced by agricultural practices (Thiollet-Scholtus and [START_REF] Thiollet-Scholtus | Using indicators to assess the environmental impacts of wine growing activity: the INDIGO® method[END_REF][START_REF] Van Der Werf | An indicator of pesticide environmental impact based on fuzzy expert system[END_REF]. I-Phy indicator scores are based on a fuzzy decision tree aggregating system and are expressed on a scale of 0 (unacceptable risk) to 10 (no risk). The reference value 7 corresponds to an acceptable risk to the environment.

Soil compaction was assessed by root percentage and soil settling level in soil cultivation profiles that were obtained once, in 2015, for each NLIVS [START_REF] Lagacherie | Spatial variability of soil compaction over a vineyard region in relation with soils and cultivation operations[END_REF]. Results were expressed as percentages from 0 (no soil settling, with pores and roots, i.e., no soil compaction) to 100 (total soil settling without lacunae or roots, i.e., totally compacted soil). Acceptable soil settling was defined as less than 20%. This level of soil compaction corresponds to the minimum space that allows vine root development. This indicator thus provides an overall measure of the impact of soil management practices. As vine plots typically include three different zones that reflect soil maintenance practices [START_REF] Lagacherie | Spatial variability of soil compaction over a vineyard region in relation with soils and cultivation operations[END_REF], soil profiles were assessed in each of these three zones: under vine rows (0.3 m wide), ploughed inter-row areas (0.5 m wide), and cover-crop inter-row areas (0.5 m wide). For each profile, soil compaction was assessed at two depths: 0-0.2 and 0.2-0.6 m. Thus, six soil compaction assessments were obtained per system.

Bacterial activity in soil was estimated by measuring the optical density of bacterial concentration in soil suspension able to degrade 31 sources of carbon over 48 h.

Bacterial molecular biomass is measured by quantitative PCR to extract soil DNA. The DNA bacterial biomass is used to evaluate the effect of soil management on the total soil microbial biomass.

Soil samples were incubated at 28°C. NH4 and NO3 concentrations were measured after 0, 7, 14, 28, and 56 days to obtain the rate of nitrogen mineralization in the soil. The available nitrogen in the soil was represented by the quantity of nitrogen mineralized in 15 days. This duration under controlled laboratory conditions is equivalent to 4 months in the vineyard; 4 months is the time required for grape bunches to mature, accumulating sugar and acids in the process.

The two indicators selected to assess biodiversity in the NLIVS were number of species present, or specific floristic richness, and relative pollination value, which provides information about this ecosystem service. Botanical surveys were performed three times per year from 2014 to 2018 at grapevine budburst, flowering, and bunch closure in each of the 11 systems. We measured floristic richness as the number of plant species present on a 500 m 2 plot. All test areas were located centrally within the system area in order to avoid edge effects [START_REF] Geiger | Persistent negative effects of pesticides on biodiversity and biological control potential on European farmland[END_REF].

The relative pollination value was calculated based on the pollination values of the species identified in the botanical survey. These were assigned following [START_REF] Ricou | A vegetation-based indicator to assess the pollination value of field margin flora[END_REF], in which a score of 0 represents a plant with no pollination value and 10 represents high pollination value, based on the domestic bee. The reference value of 3.5 is specified as representing acceptable pollination interest.

The indicator was calculated as the percentage of the species found in each botanical survey that had a pollination value greater than 3.5.

Agronomic quantitative and qualitative indicators

Vine vigour was measured by weighing winter-pruned wood. In each NLIVS and for each year, the grapevines of four sub-plots were hand-pruned in December. Each sub-plot is a 10-vine-group. The sub-plots were selected according to resistivity (e.g. water supply in soil) map of the plot to represent the intra-plot variability in vine phenology according to potential water stress. The cut branches were collected and weighed immediately according to the method used by [START_REF] Ripoche | Changing the soil surface management in vineyards: immediate and delayed effects on the growth and yield of grapevine[END_REF]. The yield per vine was measured at harvest in each NLIVS. The system yield per hectare was then calculated using the actual planting density recorded for that NLIVS and year.

Damage caused by fungi on grapes at harvest is a good proxy for the effectiveness or failure of the plant protection strategy and is connected to the TFI and I-Phy indicators (section 2.2.1). Experts from local extension services assessed damage to grape bunches due to powdery mildew and grey rot at harvest by visual observation. The damage rating for each of these two diseases consisted of the number of bunches with any damage due to that disease as a percentage of the total bunches on that vine. Then, again for each disease separately, the percentage of damage was assessed within each damage cluster. For each cluster, the intensity was multiplied by the relevant frequency rating to yield the powdery mildew and grey rot intensity indicators as percentages.

The reference for acceptable powdery mildew and grey rot intensity was defined as a maximum of 10% per cluster. The means across all ten-vine-groups in each NLIVS were then calculated to obtain a single value per system for each year.

Sugar content and total acidity were measured in the juice of the same 10-vine-groups at harvest.

The sensory indicator, here used to measure overall wine quality, was based on conventional descriptive analysis as described by [START_REF] Cadot | Characterisation of the sensory representation of the conceptual and the perceptual typicality for wines related to terroir. An application to red wines from Loire Valley[END_REF]. The assessment was performed by an expert sensory panel composed of an average of 17 judges connected to the wine research sector, who were selected based on their availability and interest. A simplified set of sensory descriptors was predefined using the descriptors of [START_REF] Jourjon | Comparaison d'échelles de notation utilisées lors de l'évaluation sensorielle de vins[END_REF]. Wines were assessed in duplicate in a Williams Latin Square arrangement to capture presentation order and carry-over effect. Wines were assessed by comparing them to the Alsace wine reference. Testing was performed blind. The reference sensory indicator value used was 5/10, corresponding to the quality required for the Protected Designation of Origin (PDO) wine standard, which uses a scale from 0 (unacceptable) to 10 (very good). This measure is a summary of the agronomic performance result of the studied systems, i.e., quantity and quality of juices to make PDO wines.

Costs and social indicators

The economic assessment was based on the profitability of the grapevine system before winemaking.

This indicator, semi-gross margin, was calculated per NLIVS per hectare as grape sales revenue minus the cost of production, including workforce, pesticides, fertilisers, and equipment, in euros [START_REF] Keichinger | SOECO: Socio-economic indicators for viticulture and innovative cultural systems[END_REF][START_REF] Meylan | Combining a typology and a conceptual model of cropping system to explore the diversity of relationships between ecosystem services: The case of erosion control in coffee-based agroforestry systems in Costa Rica[END_REF]. Vineyard profitability, which is the net economic result including farm costs. The reference value of this economic indicator is that of a field of the vineyard without pesticide reduction, for each NLIVS. It is also important to evaluate economics at the vineyard scale in order to judge and discuss the adoptability of NLIVS by winegrowers. Vineyard profitability is expressed in euros. There is no reference at this scale because of the very large diversity of the studied systems.

The human capital indicator assesses social factors relating to vineyard workers. It has three components: (i) labour-intensiveness: arduousness of the labour involved; (ii) pesticide risk: the health risks of the relevant pesticide; and (iii) occupational health: safety at work. The labour element is measured as the mean time spent in repetitive work, painful postures and subject to mechanical vibration, compared to a reference from the French health system. EUROPOEM data [START_REF] Van Hemmen | EUROPOEM, A Predictive Occupational Exposure Database for Registration Purposes of Pesticides[END_REF] were used to evaluate health risks by estimating exposure during pesticide preparation and spraying, considering whether personal protection equipment was used. Pesticide sub-indicator considers only risk to the operator. Finally, the safety element uses measures of worker education and protection while using mechanical equipment. The human capital indicator result aggregated these three risks using fuzzy-logic decision trees, producing a scale value from 0 (unacceptable) to 10 (fully acceptable) (Thiollet-Scholtus and [START_REF] Thiollet-Scholtus | Using indicators to assess the environmental impacts of wine growing activity: the INDIGO® method[END_REF]. More details about this indicator calculation are available in [START_REF] Keichinger | SOECO: Socio-economic indicators for viticulture and innovative cultural systems[END_REF]. This indicator was calculated for only one year (2015) because the practices do not change every year. This indicator was not calculated for E, F, J, or K NLIVS because their vines were planted in 2014.

The reference for the human capital indicator is the value for a field of the farm without pesticide reduction. Considering human capital is essential when evaluating systems because it will be decisive for the dissemination of NLIVS after validation of their performance.

Statistical analysis

For indicators determined more than once during the six-year experimental period, means were calculated to compare the NLIVS and the assessment criteria, producing a single value per NLIVS for the 2013-2018 period. A boxplot was used to show the distribution of the annual data for each indicator and each NLIVS. Judges and replicates of the sensory data are described by Thiollet-Scholtus et al. (2020). For sensory data, one-way analysis of variance was performed, with wine as the factor and judges as replicates. For sensory attribute with an effect of wine, a Newman-Keuls test was used to determine the significance of differences between group means (P = 0.05) according to the method described by [START_REF] Cadot | Characterisation of the sensory representation of the conceptual and the perceptual typicality for wines related to terroir. An application to red wines from Loire Valley[END_REF].

Statistical analysis was performed using XLSTAT-Pro software (ver. 2009; Addinsoft, Paris, France).

Results: NLIVS sustainability results according to targeted goals

There was a very clear decrease in TFI-total (i.e., both total pesticide used and biocontrol inputs used) for all NLIVS, compared to the local mean of 10.9 [START_REF] Pujol | Apports de produits phytosanitaires en viticulture et climat : une analyse à partir des enquêtes pratiques culturales[END_REF]. Only 4 of the 54 values obtained exceeded this value. The overall mean of TFI-total scores for all systems and all years was only 5.5.

Five NLIVS (C, H, I, J and K) had a TFI-total less than 5.5 for several consecutive years (Fig. 1-A).

Individually, fungicide and biocontrol TFI performance lay below the local mean value for all NLIVS (Fig. 1-B). The TFI-biocontrol and TFI-total indicators were close to zero for systems J and K because they used resistant grape varieties, which were associated with minimal pesticide and biocontrol management (Fig. 1-C).

The I-Phy indicator results were satisfactory for all of the systems studied. Mean I-Phy ranged from 9-10 for all NLIVS (Fig. 1-D), which lay above the acceptable value of 7/10. All results for individual years exceeded 7, varying from 7.3 (system D in 2014) to 10 (systems H, I and K). This confirms that winegrowers are minimizing the environmental risk of pollution by pesticides (Fig. 1-D).

Levels of copper use in the NLIVS were low, with an overall mean of 0.74 kg.ha -1 .y -1 , and a maximum of 3.04 kg.ha -1 .y -1 , compared to the maximum authorized use in Europe of 4 kg.ha -1 .y -1 . This confirms that our NLIVS managed to substantially reduce all vine-protection inputs including copper (Fig. 1-E).

The soil compaction results suggested that annual ploughing does not lead to high compaction of the soils of the NLIVS (Fig. 2-A). Under the rows, the topsoil (0-0.2 m) in all NLIVS had a compaction indicator of less than 20%, which was thus considered not compacted and satisfactory. In the topsoil of ploughed inter-rows, soils were compacted only in systems D and B, which had 40% and 80% soil compaction, respectively. These systems retained some herbicide spraying; more frequent spraying using tractors may have caused this additional compaction. The topsoil of the cover-crop inter-rows was not compacted (less than 20%), except in systems A, B, F and I. In F, it was due to spraying protection productions on vines planted in 2014, which required heavy tractor traffic. In I, it was due to spraying frequently with low doses of pesticides. In A and B, where compaction was the highest (80%), it was due to optimizing pesticide spraying, i.e. dividing the total amount of pesticide sprayed among several applications, which increased the frequency of tractor passes. The deeper soil layer (0.2-0.6 m) under the vine rows was more compacted than the topsoil; only systems F, I, and J systems had less than 20% compaction. Deep soil compaction was due to specific vine management activities such as grubbing-up and planting. As there were no clear relationships between deep soil compaction and NLIVS, and our NLIVS were based more on yearly management changes than on these practices, we assumed that this deep soil compaction is not directly related to the NLIVS types but with agricultural practices before 2013 (Fig. 2-A).

Indicator results for bacterial activity in the soil and bacterial biomass were satisfactory for all NLIVS (Fig. 2-B, 2-D), as were those for the speed of nitrogen mineralization in the soil (Fig. 2-C).

In the first year of measurement ( 2014), the rate of available nitrogen was approximately 13 mg kg -1 in all systems. In 2015, systems E and F had higher values, and system G had an atypically high value (greater than 65 mg kg -1 ). We hypothesized that this was due to mulching with hardwood chips under the rows in October 2014. Systems E and F continued to show similar values in 2016 and 2018. The 2018 measurement in systems B and G indicated an increasing rate of nitrogen mineralization (Fig. 2-E).

The mean relative pollination value was 42%, ranging from 24-58% (Fig. 3-A). Mean floristic richness was 65 species, varying from 39-94 species. There were no significant differences among the 11 systems studied, suggesting that none of the NLIVS had a direct effect on these indicators (Fig. 3-B).

Vine vigour was satisfactory for all NLIVS, with a mean score of 0.63 kg vine -1 (Fig. 4-A) compared to the national average of 0.3-0.7 kg vine -1 in 2018, as was vine yield, with a mean yield of 12,058 kg ha -1 (Fig. 4-B).

Disease indicators were also satisfactory for all NLIVS. For powdery mildew, all indicator values lay below 11% of bunches (Fig. 5-A), which corresponds to winegrowers' production objectives. For grey rot, the indicator values lay below 12% of bunches, which corresponds to winegrowers' production objectives, in 51 of the 54 measurements (Fig. 5-B). Winegrowers were able to minimize risk to quality; thus, the risk taken in adopting NLIVS did not decrease crop quality.

The juice sugar, at 119-240 g L -1 (Fig. 6-A), and the total juice acidity, at 3.1-10.2 g H2SO4 per L (Fig. 6-B), were both satisfactory for all NLIVS according to the PDO specification.

The sensory evaluation of wines from the NLIVS was also sufficient to meet the PDO standard.

Every wine studied scored from 4/10 to 6/10 (Fig. 6-C). It suggests that none of the NLIVS had a direct effect on this outcome.

The semi-gross margins at the system scale varied greatly among systems, ranging from a loss of €9000 to a gain of €6585 per year (Fig. 7-A).

Vineyard profitability also varied greatly for the annual periods measured, ranging from a loss of €12,000 to a gain of €3000 per year (Fig. 7-B). The NLIVS were found to be labour-intensive, with unsatisfactory typical indicator values of approximately 5 on a scale of 0-5. Innovations related to the decrease in pesticide spraying appear to have increased the labour needed to change viticulture practices. However, the human working time of NLIVS remained within the average working time of viticulture systems without innovation. Thus, the results suggest that this should not prevent implementing NLIVS in vineyards.

The arduousness risk indicator results were unsatisfactory. Almost all NLIVS scored zero, except for system B (Fig. 8), which scored 10. System B reduced all of the factors considered in the arduousness risk indicator (noise, low back pain, and musculoskeletal disorder) due to more frequent use of mechanization than the other NLIVS.

The pesticide risk indicator results were unsatisfactory, 0-4.3 on a scale of 0-10, compared to the reference value of 7. Systems A and D scored 0 (high pesticide risk to the operator) due to the toxicity of active ingredients used in these systems. The unsatisfactory scores of systems B (4.29), C (4.00), and G (4.86) were due to the rates of pesticide sprayed, while the scores of systems H (3.67) and I

(1.33) were due to the frequency of pesticide spraying (Fig. 8). These results show that the intensity of pesticide use remains a danger for the operator who runs the viticultural system, even in very lowinput systems. Even if pesticide rates are decreased and pesticides are approved by environmental certifications, there is a risk to the operator.

The security risk indicator results were satisfactory. All NLIVS scored from 8 to 10. Due to the unsatisfactory scores of most systems for pesticide risk and arduousness risk, results of the aggregate human capital indicator were not very satisfactory, as all ranged from 2.4-4.6, except for system B, which scored 9.1, compared to the reference value of 7 on a scale of 0-10. This suggests a risk of decreasing the acceptability of most NLIVS (Fig. 8).

Discussion

Relative sustainability performances of NLIVS

Encouragingly for NLIVS, the four indicators that varied along the NLIVS gradient are environmental indicators: TFI-total, TFI-fungicides, bacterial biomass, and bacterial activity in soil (Fig. 2-B).

The TFI-total results confirmed the reduction in overall pesticide use in our system classification (Table 2), from 7.69 (system A) to 0 (system K) (Fig. 1-B). The TFI -biocontrol indicator values increased with the gradient of NLIVS, from 4% (system A) to 84% (system H) or 74% (system I).

Bacterial biomass in the soil and bacterial activity in soil increased with the NLIVS gradient, from 0-1.4 × 10 12 DNA copies per g of soil per second, and from 0-1.1 (no unit), respectively.

This result is consistent with the assumption that reducing pesticide inputs has increasingly positive impacts on environmental indicators. It is consistent with the results of [START_REF] Lechenet | Reconciling Pesticide Reduction with Economic and Environmental Sustainability in Arable Farming[END_REF] and [START_REF] Reeve | Soil and winegrape quality in biodynamically and organically managed vineyards[END_REF]. Conversely, it does not agree with those of [START_REF] Döring | Organic and Biodynamic Viticulture Affect Biodiversity and Properties of Vine and Wine: A Systematic Quantitative Review[END_REF], who found no environmental difference between organic and biodynamic viticulture systems; this may be due to the few sustainability indicators they used, none of which measured bacterial activity in the soil.

Another notable result is that the copper rate decreased according to the NLIVS gradient. Systems I, J and K depended little on copper input, at 0.42, 0.08, and 0.0 kg ha -1 y -1 , respectively, which remained stable over time. In contrast, systems A, B, C, D, F, and G depended more on copper input, with higher variability (Fig. 1-E).

Other environmental assessment results, even if they do not clearly discriminate among the NLIVS, were also satisfactory for NLIVS sustainability, as mentioned.

The results for growth and yield (Fig. 4), disease incidence (Fig. 5), juice quality, and wine sensory characteristics (Fig. 6) did not discriminate among the NLIVS. These results are consistent with the assumption that decreasing environmental impacts of a system does not decrease the quantity and quality of the grapes and wine produced. This contrasts with results of [START_REF] Döring | Organic and Biodynamic Viticulture Affect Biodiversity and Properties of Vine and Wine: A Systematic Quantitative Review[END_REF], who reported a decrease in vine yield and more grey rot attacks in organic systems than in conventional ones.

Economic indicator variation along the NLIVS gradient showed that semi-gross margin and vineyard profitability increased from systems G to K. The results suggest that the least cost-effective NLIVS are the intermediate systems B, C, and D, in which only technical changes were implemented rather than a complete redesign of the system. These systems can be considered hybrids, in which the transition toward very low-input is incomplete. They relied mainly on reducing the rate of and dividing pesticide applications (i.e., increasing pesticide efficiency) to decrease pesticide use, rather than whole-system redesign, including organizational changes, which characterized systems F to K [START_REF] Hill | Conceptual frameworks for the transition from conventional to sustainable agriculture[END_REF] (Fig. 7).

The human capital indicator did not clearly improve among NLIVS. Except for the pesticide risk indicator, arduousness and security did not seem to vary much among the systems (except for system B). While replacing conventional pesticide practices with more environmentally friendly ones reduces environment impact, it does not seem to reduce risks to the operator. As all of the NLIVS still use some kind of pesticide, they still present a risk to the operator.

Benefits of the NLIVS

With the growing evidence of pesticide toxicity [START_REF] Damalas | Understanding benefits and risks of pesticide use[END_REF] and overall societal distrust in such agricultural practices, winegrowers should rapidly transition towards drastically reducing pesticide use. Assessing and comparing these NLIVS allows a range of pesticide-reduction solutions to be proposed to winegrowers. The relative performances of these NLIVS highlight that progressive and radical pesticide reduction is possible without large loss of yield or quality. However, one should recall that pesticide reduction is most effective when the entire farming system is redesigned. Our study showed that systems J and K, the redesigned systems, are those that have the best environmental performances while keeping production and quality performances at an acceptable level and ensuring good economic results. With their very low use of synthetic pesticides, copper, and machinery, these systems are also more resilient to economic and climatic changes [START_REF] Dardonville | Influence of diversity and intensification level on vulnerability, resilience and robustness of agricultural systems[END_REF].

Redesigning vine growing production systems is not easy, as the complexity of system management generally increases [START_REF] Merot | Converting to organic viticulture increases cropping system structure and management complexity[END_REF], as does the load or arduousness of the work. The results tend to show that using resistant grape varieties eases management of these NVLIS. This genetic innovation seems to be a good mechanism for transitioning towards agro-ecological vine systems.

Which indicators to assess NLIVS sustainability?

Agronomic performance indicators (i.e. yield and vigour) and qualitative wine performance (i.e. juice sugar, juice total acidity, and wine sensory characteristics) seemed to describe the winegrowers well.

The results showed that NLIVS achieved the standards required by the PDO specification for the area in which they were implemented. Thus, they support the hypothesis that NLIVS can produce grapes that can claim an Alsace PDO.

Two indicators seem questionable for assessing NLIVS sustainability. Their lack of variation may indicate that they have limited sensitivity and may not reflect an absence of effects. For example, the complex aggregate indicator I-Phy, developed in the 2000s to assess diverse existing viticulture systems, was unable to discriminate among the NLIVS, all of which scored above 7. Most of these sustainability indicators were developed to discriminate between conventional and more sustainable cropping systems. Thus, they might be under-equipped to discriminate among different strong "alternative" viticulture systems. To discriminate among NLIVS now and in the future, indicators should be adapted and improved. Indicators could be adapted and improved by redefining their thresholds, references, and limits, which are parameters that greatly influence their sensitivity [START_REF] Bockstaller | A tool to design fuzzy decision trees for sustainability assessment[END_REF]. New indicators may also need to be built that consider new properties of future NLIVS. For example, from a cost perspective, the high variability in economic performance suggests that not all of the NLIVS in our study are sustainable. This instability could hinder adoption of NLIVS by winegrowers. However, a simple economic assessment may be insufficient to assess the economic viability of NLIVS. Future economic assessments could benefit from additional detail and a wider range of factors, such as investment and depreciation rates.

Generality of NLIVS and assessment results

The NLIVS within this study were designed and experimented with in Alsace. Generally, as pesticide reduction can be a shared goal, agricultural production systems should be designed for local contexts [START_REF] Meynard | Designing coupled innovations for the sustainability transition of agrifood systems[END_REF]. Because of its soil and climatic context, Alsace has wine production conditions that lay between those of regions with a very strong oceanic influence (e.g. Loire valley in France, Porto area in Portugal) and those with a strong continental influence (e.g. Tokay area in Hungary).

These NLIVS could be developed in other regions by adapting them to the local soil and climatic conditions. In an oceanic climate, the main changes would be to maintain higher rates of copper application, as winegrowers may be less inclined to decrease it due to the higher pathogen pressure. In a continental climate, winegrowers could opt for more inter-row cover-crops in winter only, as the water stress is stronger in the summer. (R1-1)

Regarding the socio-technical context, Alsace benefits from a PDO defined by a set of characteristics that include authorized vine varieties and the trellis system. When exporting a specific vine system, one should be aware of the consistency of these socio-technical characteristics, especially when using pathogen-resistant varieties. These new varieties may not be eligible in other PDOs or specific wine appellations (e.g. Vin de France). Using a specific vine variety (e.g. Chardonnay) more sensitive to fungi may require more pesticide spraying, which would worsen environmental assessment results (e.g. TFIs, I-Phy, copper rate). Nonetheless, other practices, such as the type of trellis (e.g. pergola, buckets) may not be large obstacles to generalizing NLIVS, as they do not influence pathogen pressure.

Conclusion

The assessment of NLIVS performance covered all aspects of system sustainability: environmental, agronomic, social, and economic. The results demonstrate that it is possible to combine good environmental and agronomic performances, with a TFI reduced by up to 89% and more moderate socio-economic performance. NLIVS are thus sustainable according to many diverse indicators and can also remain resilient over six consecutive years.

Assessing NLIVS with a large number of indicators is useful. Such sustainability assessment, simultaneously considering agronomy, environment, social factors, and economic performance, is essential for identifying obstacles and mechanisms that influence adoption of NLIVS by winegrowers.

Social and economic assessment needs further improvement to encourage broad and sustainable adoption of NLIVS by winegrowers while maintaining a high level of agronomic and environmental performance. The information obtained contributes to winegrower assessments of potential risks of transitioning their systems to agro-ecological viticulture.

Consequently, NLIVS have multiple benefits: i) they decrease environmental impacts while maintaining the profitability and agronomic performance of the system; ii) they are essential for adapting viticulture to pesticide regulations; and iii) the diversity of the 11 NLIVS, from efficiency to redesign, makes it possible to disseminate them to other vineyards using feasible adaptations. For 'herbicides', there is a decrease in their use on the surface of the plot, starting with use everywhere (xxx), then removing use on half of the inter-rows (xx), then on all inter-rows (x), and ending with no use (_). The gradient of notation is reversed for 'plowing' and for 'crop soil cover'. For 'copper', there is a decrease of rate use on the surface of the plot, starting with the reference rate (xxx) according to E-phy database, then by dividing the reference rate by at least 2 (xx), then by dividing the reference dose by at least 5 (x), and finally by completely eliminating the use of copper (_). The gradient is the same for 'Sulfur' and 'Chemical'. Tek: technical, Org: organizational, Re: redesign.

AFigure 2 .

 2 Figure 2. Soil assessment (A, B, C, D, E). For each indicator and new low-input vine system: dots show the distribution of annual observations, red diamonds show means, and whiskers show the minimum and maximum.

Figure 3 .

 3 Figure 3. Biodiversity assessment (A, B). For each indicator and new low-input vine system: dots show the distribution of annual observations, red diamonds show means, and whiskers show the minimum and maximum.

Figure 6 .

 6 Figure 6. Juice quality and sensory characteristics assessment (A, B, C). For each indicator and new low-input vine system: dots show the distribution of annual observations, red diamonds show means, and whiskers show the minimum and maximum. A Juice sugar in g L -1B Juice total acidity in H2SO4 g L -1 C Wine sensory characteristics (no unit)

Figure 8 .

 8 Figure 8. Social acceptability assessment (A, B, C, D). For each indicator and new low-input vine system: black crosses show the distribution of observations in 2015.

Table 1 . Characteristics of New Low Input Vine Systems.

 1

	Characteristics	Nature
	Variety Riesling, pinot blanc, pinot gris or resistant varieties
	Root stock SO4, 3309, or 161-49
	Vine age From 5 to 42 years-old
	Winter pruning practice Double Guyot
	Slope From 0% to 15%
	Soil type	Brown soil, granite alluvium soil, stony and silt clay soil, clay loam soil or loamy sandy soil
	Environmental specification Integrated, organic or biodynamic
	PDO certification 'Alsace', 'Crémant' or 'Grand Cru'

Table 2 . Gradient of intended reduction in pesticide use in new low input vine systems (NLIVS).

 2

Table 3 . Characteristics of assessment indicators.

 3

	Indicators	Reference	Reference comment	Unit	Variation range	Number of original measures
		Local average: 10.9
	TFI-total	in 2013. National average: 14.7 in	National survey every 6 years gives the local and national averages.	no unit		11 systems, 6
		2013.			0 to 12.7	years, 51 scores
	TFI-fungicides	Local average: 9.8 in 2013	National survey every 6 years gives the local and national averages.	no unit	0 to 11.7	11 systems, 6 years, 51 scores
	TFI-biocontrol/TFI-total		_	%	0 to 100%	11 systems, 6 years, 51 scores
	I-Phy	Integrated viticulture: 7/10	INDIGO(R) scale	no unit	0 to 10	11 systems, 6 years, 45 scores
	Copper rate	Local average: 1.6 kg.ha-1.year.-1 in 2013	European and French authorized maximum is 4 kg.ha-1.year-1	kg.ha-1.year-1	0 to 3.0	11 systems, 6 years, 51 scores
			Scale from 0 (no settling) to 100% of
	Soil compaction	No local average	compacted soil (correspondgin to ro vine root in the soil).	no unit	0 to 100%	11 systems, 1 year (2015), 60 scores
	Nitrogen bacteria					11 systems, 3 years
	activity in soil					(2014, 15, 18), 20
					0.1 to 1.1	scores
	Nitrogen bacteria biomass in soil				1,4E+12 to 2,6E+10	11 systems, 3 years 15, 18), 28 scores
	Speed of nitrogen					11 systems, 3 years
	mineralization in			mgN.kgDM-1		15, 18), 28
	the soil at veraison				0.0 to 0.1	scores
	Amount of					11 systems, 3 years
	available nitrogen			mgN.kgDM-1		15, 18), 28
	in soil at veraison				1.5 to 69.0	scores
	Relative pollination value			no unit	24.4 to 58.0	11 systems, 6 years, 51 scores
	Total floristic richness			no unit	39.0 to 94.0	11 systems, 6 years, 51 scores
	Vine vigor	Winemaker personnal goal	no PDO specification	kg.vine-1.year-1	0.2 to 1.0	11 systems, 6 years, 47 scores
	Yield	Winemaker personnal goal	PDO specification is the maximum	kg.ha-1.year-1	2240.7 to 28913.3	11 systems, 6 years, 43 scores
	Powdery mildew
	intensity on bunches (%) at	Local pest pressure	No regulatory reference	%		11 systems, 6
	harvest				0% to 10.7%	years, 47 scores
	Grey rot intensity
	on bunches (%) at	Local pest pressure	No regulatory reference	%		11 systems, 6
	harvest				0% to 46.2%	years, 47 scores
	Juice sugar rate	Winemaker personnal goal	PDO specification is the maximum	g.L-1	119.9 to 240.2	11 systems, 6 years, 43 scores
	Juice total acidity	Winemaker personnal goal	no PDO specification	H2SO4 g.L-1	3.1 to 10.2	11 systems, 6 years, 43 scores
	Wine sensory characteristics	Alsace PDO average (5/10)	no PDO specification	no unit	0 to 11.7	11 systems, 6 years, 43 scores
	Profitability1	Winemaker personnal goal	Semi gross margin at system scale	euros	_9000 to 6585	11 systems, 1 year (2015), 11 scores
	Profitability2	Winemaker personnal goal	Net economic result including farm costs euros	_11387 to 2813	11 systems, 1 year (2015), 11 scores
	Human capital	No reference	_	no unit	0 to 10	11 systems, 1 year (2015), 11 scores
	Penibility	No reference	_	no unit	0 to 10	11 systems, 1 year (2015), 11 scores
	Pesticides	No reference	_	no unit	0 to 10	11 systems, 1 year (2015), 11 scores
	Security	No reference	_	no unit	0 to 10	11 systems, 1 year (2015), 11 scores

Acknowledgements

This study was supported by the APCA [X2IN68VI] and Alsace region in the PEPSVI project. We are grateful to technical help in obtaining the data (in alphabetical order): P. Audema, C. Bailly, S.

Chaumonnot, C. Klein, G. Lemarquis, S. Ribeiro, C. Schneider, J. Weissbart and SEAV, INRA, 2018.

Viticulture Facility, doi: 10.15454/1.5483269027345498E12. Thanks also go to Rui Catarino for helpful scientific discussion about the results.

Declaration of Competing Interest

None.


Myriam Boulmedais

Marion Monperrus

M Ph

Elise Corbel

Pauline Blanc-Petitjean

Linda Lassel

Rémi Béranger

Krystel Nyangoh Timoh

Isabelle Enderle

MD Maela Le Lous
email: maela.le.lous@chu-rennes.fr

Predictive value of head-perineum distance measured at the initiation of the active second stage of labor on the mode of delivery: a prospective cohort study. -EchoPe

Keywords: intrapartum ultrasound, transperineal ultrasound, head-perineum distance instrumental delivery, caesarean section, active second stage of labor

Objective

The objective was to assess the predictive value of head-perineum distance measured at the initiation of the active second stage of labor on the mode of delivery.

Material and Methods

It was a prospective cohort study in an academic Hospital of Rennes, France, from July 1, 2020 to April 4, 2021 including 286 full-term parturients who gave birth to a newborn in cephalic presentation. A double-blind ultrasound measurement of the headperineum distance was performed during the second phase of labor within five minutes after the onset of pushing efforts. The primary outcome was the mode of delivery (spontaneous vaginal delivery versus instrumental vaginal delivery or cesarean section). We performed a multivariate analysis to determine the predictive value of the head-perineum distance by adjusting on potential confounders.

Results

Overall, 199 patients delivered by spontaneous vaginal delivery, 80 by instrumental vaginal delivery, and seven by cesarean section. The head-perineum distance measured at the beginning of pushing efforts was predictive of the mode of delivery with a threshold at 44 mm (crude: sensitivity = 56.8% and specificity =79.3%; adjusted: sensitivity =79.4% and specificity=87.4%). The risk of medical intervention is higher when the head-perineum distance is greater than 44 mm with an adjusted OR of 2. 78 [1.38; 5.76].

Conclusion

The head-perineum distance measured at the initiation of the active second stage of labor is predictive of the mode of delivery. Head-perineum distance below 44mm predicts a vaginal delivery with the best diagnostic performance, and optimizes the time to start pushing efforts.

Introduction

In some european countries, pushing efforts are usually starting after the diagnosis of engagement, during the second stage of labor, while in some other countries, pushing efforts usually start at diagnosis of complete cervix dilation at the beginning of the second phase. There is no clear difference in terms of spontaneous vaginal delivery between the two methods although delayed pushing tends to induce shorter pushing efforts, but longer second stage of labor [START_REF] Mascio | Delayed versus immediate pushing in the second stage of labor in women with neuraxial analgesia: a systematic review and meta-analysis of randomized controlled trials[END_REF][START_REF] Lemos | Pushing/bearing down methods for the second stage of labour[END_REF] .

Longer duration of the second stage of labor seems positively correlated with higher rate of chorioamniotitis, lower umbilical artery pH and higher risk of post-partum hemorrhage [START_REF] Lemos | Pushing/bearing down methods for the second stage of labour[END_REF] .

Starting pushing efforts too late might induce unnecessary longer duration of the second stage of labor. On the other hand, starting pushing efforts too early might increase maternal exhaustion, and thus the risk of instrumental deliveries (forceps, vacuum, spatulas) [START_REF] Lemos | Pushing/bearing down methods for the second stage of labour[END_REF] .

Instrumental deliveries cause greater perineal injuries [START_REF] Pergialiotis | Risk factors for severe perineal trauma during childbirth: An updated meta-analysis[END_REF] . On the neonatal side, instrumental deliveries may lead to short-term morbidity [START_REF] Ghidini | Neonatal complications in vacuum-assisted vaginal delivery: are they associated with number of pulls, cup detachments, and duration of vacuum application?[END_REF] , especially when combined with a sequential cesarean section [START_REF] Mcdonnell | Determinants and Outcomes of Emergency Caesarean Section following Failed Instrumental Delivery: 5-Year Observational Review at a Tertiary Referral Centre in London[END_REF] .

Today, the diagnosis of engagement is based solely on the digital examination by the midwife or the physician. However, studies have highlighted its subjectivity and its high inter and intraobserver variability [START_REF] Dupuis | Birth simulator: reliability of transvaginal assessment of fetal head station as defined by the American College of Obstetricians and Gynecologists classification[END_REF][START_REF] Sherer | Intrapartum fetal head position II: comparison between transvaginal digital examination and transabdominal ultrasound assessment during the second stage of labor[END_REF] . In contrast, ultrasound in labor has been found more accurate and objective in assessing fetal head station and position [START_REF] Malvasi | Occiput posterior position diagnosis: vaginal examination or intrapartum sonography? A clinical review[END_REF][START_REF] Tse | Labor progress determined by ultrasound is different in women requiring cesarean delivery from those who experience a vaginal delivery following induction of labor[END_REF] . The use of transperineal ultrasound in the delivery room has been used to intent reduce maternal-fetal morbidity [START_REF] Chaemsaithong | Factors that affect ultrasounddetermined labor progress in women undergoing induction of labor[END_REF] . It may help to confirm fetal presentation, but also the fetal head station in the pelvis [START_REF] Eggebø | Prediction of labor and delivery by transperineal ultrasound in pregnancies with prelabor rupture of membranes at term[END_REF] .

The head-perineum distance measured in transperineal ultrasound is one of the parameters proposed as an aid in the diagnosis of fetal head station and as a predictor of successful instrumental delivery [START_REF] Eggebø | Descent of the presenting part assessed with ultrasound[END_REF][START_REF] Neto | Assessment of the angle of progression and distance perineum-head in the prediction of type of delivery and duration of labor using intrapartum ultrasonography[END_REF][START_REF] Magnard | Instrumental delivery with perineum-fetal head distance >55 MM on ultrasound[END_REF] . Moreover, it is admitted that an instrumental delivery can be realized only on engaged fetuses, under penalty of substantial risk excess of maternal-fetal morbidity [START_REF] Sentilhes | Indications and prerequisites for operative vaginal delivery: when, how and where?[END_REF] . Performing instrumental delivery on a fetal station greater than 55 mm on transperineal ultrasound has been described as more likely to result in failure and therefore in emergency cesarean section [START_REF] Magnard | Instrumental delivery with perineum-fetal head distance >55 MM on ultrasound[END_REF] .

We thus surmised that a reliable assessment of the fetal head station may help to assess the timing and likelihood of successful pushing.

Our primary objective was to determine whether the head-perineum distance measured at the beginning of pushing efforts is a predictive factor of the mode of delivery.

Methods

Design

We conducted a prospective, observational study at the University Hospital of Rennes, France from July 1, 2020 to April 4, 2021.

Population

Women at term (≥37 weeks of gestation) about to deliver singleton vertex-presenting fetuses were recruited to the study when they approached full cervical dilatation and before the beginning of pushing efforts.

Women were excluded from the study if the fetus was suspected of having major malformations. Data collection were obtained through the medical record: maternal age, gestational age, body mass index (BMI), mode of labor onset, oxytocin augmentation, length of the second stage, birthweight, and 5-minute Apgar score. Maternal and neonatal complications included intrapartum fever (≥38°C), postpartum hemorrhage, need for blood transfusion, and third-or fourth-degree perineal tear. The study protocol was approved by an ethic committee approval « CPP ILE DE FRANCE V » (N°2020-A00633-36). Women received information on the study objectives and protocol when they entered the maternity ward. Their non-opposition was collected in their medical file. Women were free to discontinue their participation in the study at any moment, without justification.

Methods

The measurement of the head-perineum distance was performed for each patient at the beginning of pushing efforts. The head-perineum distance was measured in millimeters by transperineal ultrasound (model: "T-LITE" device, "sonoscanner" company, probe model PR50, frequency 2-5 MHz). An OB/GYN resident previously trained to the technique was called to perform the transperineal ultrasound just before the beginning of pushing efforts for research purposes. It was agreed that the residents would be called only during working hours (8am-8pm).

The evaluation of the head-perineum distance was carried out in the dortholithotomy position, empty bladder, at the initiation of the active second stage of labor, within the five minutes preceding the onset of pushing efforts. The abdominal ultrasound probe, covered by a sterile glove, was placed transversally on perineum, without support, without compression and between contractions. The calipers were positioned "on to on" from the outer edge of the ultrasound probe marker to the outer edge of the fetal bone shelf. The result of the measurement was not communicated to the patient, nor to the midwife performing the delivery (double blind).

The operator performing the measurement was not informed of the clinical diagnosis of fetal head station. If necessary, a senior obstetrician was called and the indication of an instrumental delivery or a caesarean section was left to his discretion.

Statistics analysis

The minimum number of subjects was estimated using NQuery software, taking into account a power of 80% to detect an OR ≥ 2 when the head-perineum distance is at one standard deviation above the mean, assuming a normal distribution of this variable, a proportion of obstetrical intervention (instrumental delivery or/and cesarean section) of 12%, and a correlation coefficient (rho) of the variables included in the model equal to 0.3. A sample size of 267 women met the objective. Assuming that approximately 5% of the measures could not be analyzed because of missing data, the number of women to be included was increased to 280. The primary outcome was the mode of delivery (spontaneous versus instrumental/cesarean). To meet the primary objective, we performed a univariate analysis using the Student "t" test. The analysis was completed by a multivariable logistic regression model to determine the predictive value of the head-perineum distance.

The model included variables known a priori to influence delivery mode [START_REF] Hjartardóttir | Fetal descent in nulliparous women assessed by ultrasound: a longitudinal study[END_REF][START_REF] Dall'asta | Prediction of spontaneous vaginal delivery in nulliparous women with a prolonged second stage of labor: the value of intrapartum ultrasound[END_REF][START_REF] Tuuli | Immediate Compared With Delayed Pushing in the Second Stage of Labor A Systematic Review and Meta-Analysis[END_REF][START_REF] Hadad | Intrapartum ultrasound at the initiation of the active second stage of labor predicts spontaneous vaginal delivery[END_REF][START_REF] Torkildsen | Prediction of delivery mode with transperineal ultrasound in women with prolonged first stage of labor[END_REF] : prepregnancy BMI of the patient, parity, newborn's birth weight. Additional variables were explored as potential confounders: maternal age, past history of cesarean, induced labor, gestational age at delivery, oxytocin dose received, length of second labor phase, existence of fetal heart rate abnormalities during pushing efforts, fetal presentation at beginning of pushing efforts, abnormalities of cardiac fetal heart rate while pushing. These were manually selected when associated at p<0.25 in univariate analysis with the exposure and the variable of interest.

We then excluded some variables based on a backward selection, selected on the Akaike Information Criterion (AIC).

Variables finally included in the multivariable model were: pre-pregnancy BMI of the patient, parity, newborn's birth weight, maternal age at gestation, past history of cesarean, length of second labor phase and existence of fetal heart rate abnormalities during pushing efforts. The calibration of the model was evaluated by the Hosmer-Lemeshow test. The accuracy of prediction of the mode of delivery was determine by using a receiver operating characteristic (ROC) curve analysis. The area under the curve (AUC) was calculated with the 95% confidence interval (CI), and the best cutoff was derived from the discriminatory AUCs of those who delivered spontaneously and from those who had instrumental delivery/caesarean section. We performed an internal validation of the model by a 1000 resampling bootstrap corrected AUC calculation.

A second model adjusted for the same confounding factors was constructed by categorizing the head-perineum distance variable according to the threshold value obtained by the ROC curve (≤44 mm; >44 mm).

A p-value <0.05 was considered statistically significant. Data were analyzed using the R software (version 3.6.1).

Results

Descriptive analysis

We included 286 patients in our cohort (Figure 1 Flow-chart). A total of 199 patients had spontaneous vaginal deliveries, 80 patients had instrumental vaginal deliveries, and 7 patients had cesarean deliveries. The demographic, clinical and ultrasonographic characteristics of these patients are presented in Table 1. Respectively 63 (72.5%) women and 85 (42.8%) women were nulliparous in the group « instrumental deliveries and caesarean » (IDC) and in the group « spontaneous vaginal delivery » (SVD) (p<0.001). The average length of the second phase of labor was 157min ±57.7 for IDC group and 112.5 min ±64.8 for SVD group (p < 0.001). The duration of pushing efforts was significantly greater in IDC group (45.4min ±17.2) than in SVD group (18.1min ±13.6) (p<0.001). There were no significant differences in mean birth weight between the two groups, 3469g ±390 and 3388g ±441 respectively (p = 0.13). The mean headperineum distance measured at the beginning of pushing efforts in IDC group was 50.4mm ±9.6 while it was 41mm ±13.4 in SVD group (p< 0.001).

Primary outcome

Head-perineum distance measured at the beginning of the pushing efforts was associated with the risk of having instrumental or cesarean delivery (per 1cm increase: OR rawt =1.89 [IC95%=1.50; 2.42]) (Table 2).

The variables selected for the multivariable analysis were: BMI, birthweight, maternal age, uterine scar, duration of second stage, abnormal fetal heart rate, as continuous or categorized variables as shown in Table 2. In multivariable logistic regression analysis, the head-perineum distance measured at the beginning of pushing efforts, as a continuous variable with a normal distribution, was still significantly associated with mode of delivery with an OR of 1.74 per 1cm increase [IC95% 1.27 ; 2.46] (Table 2). Parity, maternal age, history of caesarean section, length of second labor phase, as well as existence of fetal heart rate abnormalities during pushing efforts also remained statistically significantly associated with the delivery mode (Table 2).

Derived from the ROC curves, a cutoff in head-perineum distance at 44mm best discriminated women who delivered spontaneously and those who had instrumental deliveries of caesarean.

(Figure 2. ROC curves). At the initiation of the active second stage of labor, the measurement of the head-perineum distance was greater than 44mm for 155 patients (54,1%).

In The corresponding area under the curve (AUC) was 71.62% [CI95% 65.6; 77.5] (Table 3). The AUCc obtained with the bootstrap was 87.58%. In fact, for a head-perineum distance at the beginning of pushing efforts of less than 44 mm, 86.3% of the patients gave birth by spontaneous vaginal delivery. Also, 44.5% patient with head-perineum distance greater than 44 mm had an instrumental delivery/caesarean. After adjustment for potential confounders, the threshold value of 44mm showed an area under the curve of 89.7% [CI95% 86.1; 93.3], with a calculated Youden index of 0.67, a sensitivity of 79.4% [CI95% 73.9; 84.9] and a specificity of 87.4% [CI95% 80.5; 94.3]. (Table 3).

Using a dichotomized head-perineum distance (<44mm; ≥44mm), the association with mode of delivery remained statistically significant (OR adjusted =2.78 [CI95% 1.38; 5.76]) in multivariate analysis (Table 2).

Using a subgroup analysis, in primiparous or multiparous women, the association between mode of delivery and head-perineum distance was also significant. For primigravid women, adjusted OR was 1.70 [1.14; 2.60] p= 0.008 per 1cm increase ; for multigravida women it was adjusted OR = 3.51 [1.46 11.31] p= 0.003.

We calculated the optimal cut off in those subgroups. In primiparous the optimal threshold was 38 mm (Se=90;5%; Sp= 43.5% ORa=3,32 [1.35; 8.70], p= 0.0087, AIC: 167.31). For Multiparous the best threshold was 46 mm (Se=91,6%; Sp=62,3%, ORa= 7.25 [ 0.84 ; 108.25],

, p= 0.07263. AIC: 67.33).

Discussion

In our cohort, the head-perineum distance measured at the beginning of pushing efforts was predictive of the mode of delivery. Our statistical analysis revealed a threshold value of 44mm, with a corresponding area under the curve of 89.7% [CI95% 86.06; Careful management of the second stage of labor is crucial to decrease maternal-fetal morbidity [START_REF] Mola | Factors associated with success or failure in trials of vacuum extraction[END_REF] . In practice, this means not starting pushing too early, so as not to risk maternal exhaustion and therefore the need for an instrumental delivery.

Other studies suggested that the head-perineum distance may be associated with the mode of delivery, but the measure was performed at different stages of labor. In a 2021 study from Iceland and Sweden, Hjartardottir et al. also found a significant association of head-perineum distance measured at the first and last clinical examination during labor with the mode of delivery [START_REF] Hjartardóttir | Fetal descent in nulliparous women assessed by ultrasound: a longitudinal study[END_REF] . In an Italian study by Dall'Asta et al., the head-perineum distance measured after 2 hours at full cervix dilation was also greater in cases of obstetrical interventions [START_REF] Dall'asta | Prediction of spontaneous vaginal delivery in nulliparous women with a prolonged second stage of labor: the value of intrapartum ultrasound[END_REF] . One of the notable differences between our study compared and the above-mentioned literature is the definition of the period to realize the ultrasound measurement, within 5 minutes before the beginning of active second phase. It facilitates the concrete application of our results as it may guide the midwives about when to start pushing [START_REF] Tuuli | Immediate Compared With Delayed Pushing in the Second Stage of Labor A Systematic Review and Meta-Analysis[END_REF] .

An Israeli study on 202 patients by Hadad et. al. also evaluated the interest of measuring the head-perineum distance at the beginning of pushing efforts, as well as other measures (the angle of progression, the head-symphysis distance, the head-perineum distance at rest and during pushing with contraction), in prediction of spontaneous vaginal delivery. In this study, only the angle of progression at rest and the delta AOP (difference in angle between the angle of progression during pushing and at rest) were significantly associated to the mode of delivery [START_REF] Hadad | Intrapartum ultrasound at the initiation of the active second stage of labor predicts spontaneous vaginal delivery[END_REF] .

It is interesting to note that the digital examination does not present such good diagnostic performance. Torkildsen et al. in 2011 conducted a study in patients with prolonged first stage of labor and found an area under the curve of 81% [CI95% 71; 91] for the prediction of vaginal delivery for a threshold value of head-perineum distance of 40mm, whereas it was calculated at 66% [CI95% 54; 79] for digital examination [START_REF] Torkildsen | Prediction of delivery mode with transperineal ultrasound in women with prolonged first stage of labor[END_REF] . question of a labor follow-up based on transperineal ultrasound arises. Indeed, some studies have investigated the acceptability to patients of ultrasound-based labor monitoring, and patients describe transperineal ultrasound as less unpleasant than digital examination [START_REF] Usman | Ultrasound is better tolerated than vaginal examination in and before labour[END_REF][START_REF] Chan | Is intrapartum translabial ultrasound examination painless? J Matern-Fetal Neonatal[END_REF] .

We noted differences in the technique used by authors to measure the head-perineum distance.

Indeed, some studies describe a soft tissue compression before measuring the head-perineum distance, which may be different from the technique used in our study. In other publications the transducer has been placed in the fourchette, and the soft tissue compressed until resistance against the pubic bone. In this way the influence of maternal obesity can be reduced [START_REF] Hjartardóttir | Fetal descent in nulliparous women assessed by ultrasound: a longitudinal study[END_REF][START_REF] Kahrs | Sonographic prediction of outcome of vacuum deliveries: a multicenter, prospective cohort study[END_REF] .

However, the level of compression can vary and may increase interoperator differences.

The prospective design of our study and the training of the resident ensured the good quality and homogeneity of the data collected. In addition, ultrasound measures were made in a doubleblind manner using a technique in accordance with ISUOG recommendation25. Occiput position or angle of progression could have been collected as well. However, head-perineum distance and angle of progression are independent methods and both methods gave similar mirror image patterns17.We chose the easiest measure to ensure its feasibility in our setting.

Our study also has some limitations. Indeed, we included only 14.2% of eligible patients, which led to a possible selection of patients (compared to the 2016 French national survey: more nulliparous women, more patients with induction of labor and prolonged second stage) which may have led to a higher rate of instrumental deliveries. Our rate of instrumental extractions was 27.9% in our population, and 12.1% in the French national survey. Since multiparous women give birth more quickly, we did not always have time to do our ultrasound measurement.

However, the interest of predicting delivery mode by transperineal ultrasound at the beginning of the pushing efforts is less interesting in women with a fast labor. Another limitation is that we did not collect the occiput position.

Conclusion

The head-perineum distance measured at the initiation of the active second stage of labor is predictive of the mode of delivery. Head-perineum distance below 44mm predicts a vaginal delivery with the best diagnostic performance. This measure provides women and staff additional information on whether to start pushing or to continue labor in countries practicing delayed pushing. Obstetrical teams could add this simple measurement to their routine practice to optimize the second stage of labor as a complement to vaginal examinations.

Disclosure of interests : none

  Contribution to authorship : MB participated in patient enrollment, data collection and manuscript writing MP participated in the statistical analysis EC participated in patient enrollment and data collection PBP participated in the statistical analysis LL participated in the conception of the study RB participated in the proofreading KNT participated in the proofreading IE in the conception of the study, in statistical analysis, and proofreading MLL in the conception of the study, manuscript writing and proofreading Details of patient's consent : Women received information on the study objectives and protocol. Their non-opposition was collected in their medical file.Funding : noneDetails of ethics approval :The study protocol was approved by an ethic committee approval « CPP ILE DE FRANCE V » (N°2020-A00633-36) Acknowledgement : We thank Felicity Nielson for English editing.

Figure 1 .Figure 2 .

 12 Figure 1. Flow chart HPD: head-perineum distance

Table 1 .

 1 Model adjusted on: BMI (<30 kg/m²; >30 kg/m²), parity, birth weight, maternal age, history past of caesarean section, length of second labor phase, existence of fetal heart rate abnormalities during expulsive efforts Demographic, clinic and ultrasound characteristics of the population and according to the mode of delivery.

		Spontaneous vaginal	Instrumental delivery and	p
		delivery	cesarean section	value
		N (%) or mean (SD)	N (%) or mean (SD)
		N= 199 (69.5)	N= 87 (30.5)
	Demographics
	Maternal age	29.2 (5.3)	31.3 (5.11)	0.002
	Parity			<0.001
	0	85 (42.8)	63 (72.5)
	≥ 1	114 (57.2)	24 (27.5)
	Previous cesarean	18 (9.0)	16 (18.4)	0.041
	Pre pregnancy BMI (kg/m²)			0.61
	<25	4 (2.0)	2 (2.3)
	25-30	114 (57.3)	55 (63.2)
	> 30	81 (40.7)	30 (34.5)
	Labor outcomes
	Gestational age at delivery	40.0(1.1)	40.3(1.1)	0.07
	Labor induction	48(24.1)	28(32.2)	0.2
	Total oxytocin dose (UI/L)	10.7(2.2)	11.5(3.2)	0.027
	Birthweight	3388(441)	3469(390)	0.13
	Duration of second stage	112.5(64.8)	157.4(57.7)	<0.001
	Length of pushing phase	18.1(13.6)	45.4(17.2)	<0.001
	3 and 4 degree perineal laceration	3(1.5)	10(12.5)	0.002
	Post-partum hemorrhage	11(5.5)	13(14.9)	0.016
	Fever during labor	13(6.5)	4(4.6)	0.52
	Ultrasound measurement