Predictors of conversion to cesarean section in a French cohort of 236 class III (body mass index of 40 or more) obese women attempting vaginal delivery: A restrospective multicentric study.

Background: Due to the global growth of its prevalence and its impact on patient health, obesity is considered a near-epidemic condition by the World Health Organization (WHO). Its overall prevalence has now reached 17 % in France. The impact of obesity is also a concern for pregnant women, due to the risk of maternal and fetal complications. Obesity increases the risk of cesarean delivery. However, few data are available regarding risk factors for failed attempted vaginal delivery in obese women.

Objective: The purpose of this study was to examine predictors associated with caesarean delivery among class III obese women undergoing labor.

Methods: Retrospective and multicentric cohort study at the Reims University Hospital and Troyes Hospital from 1 January 2018 to 31 December 2023. All women aged 18 years or older, with body mass index of 40 or higher at booking, with a singleton pregnancy and cephalic presentation and a vaginal delivery attempt after 24 weeks were included in the study. Demographic, obstetrical and neonatal factors were compared between women having a successful vaginal delivery and women having a cesarean delivery after a failed vaginal delivery attempt. A multivariable analysis by logistic regression was performed to evaluate the probability of a change to cesarean section.

Results: Overall, 236 obese women attempting vaginal delivery met all inclusion criteria. Among them, 166 (70.3 %) had a successful vaginal delivery, while 70 (29.7 %) had a cesarean section. Women having a cesarean delivery were more likely to be nulliparous (55.7 % vs. 33.1 %, p = 0.001), to have a weight gain of more than 9 kg during the pregnancy (32.9 % vs. 19.9 %, p = 0.028), to have a diagnosis of preeclampsia (12.9 % vs. 3.6 %, p = 0.008) and to have had induced labor (64.3 % vs. 42.2 %, p = 0.002), when compared to women with successful vaginal delivery. In multivariable analysis, pre-eclampsia was a significant risk factor for cesarean delivery (adjusted OR 4.08; 95 % CI 1.09 - 16.88; p = 0.04). In contrast, having a history of at least one successful vaginal delivery was a protective factor (adjusted OR 0.20; 95 % CI 0.08 - 0.44; p < 0.001).

Conclusion: Preeclampsia was associated with cesarean delivery in class III obese women attempting a vaginal delivery, while a history of previous vaginal delivery reduced this risk. Although vaginal delivery remains the recommended route by default in preeclampsia patients, our results suggest that obese patients with preeclampsia, especially if they are nulliparous, should be warned of the high risk of cesarean delivery.