Delivery mode and maternal-infant outcomes in women with class III obesity (BMI ≥ 40 kg/m²): a retrospective cohort study with propensity score matching

Abstract Background Obesity has become a major global public health challenge, and class III obesity (BMI ≥ 40 kg/m²) during pregnancy poses exceptional clinical risks. The optimal mode of delivery for this population remains controversial. This study aimed to compare maternal and neonatal outcomes between vaginal delivery and cesarean section in women with class III obesity at delivery using propensity score matching (PSM). Methods This single-center retrospective cohort study included 177 singleton pregnant women with delivery BMI ≥ 40 kg/m² at Xuzhou Maternal and Child Health Hospital from January 2024 to June 2026. Participants were divided into vaginal delivery (n = 29) and cesarean section (n = 148) groups. PSM was performed using 1:2 nearest-neighbor matching without replacement, incorporating 14 baseline covariates with a caliper of 0.2 × SD. The primary outcome was postpartum hemorrhage (PPH) rate. Secondary outcomes included maternal hospital stay, MICU admission, neonatal birth weight, macrosomia, Apgar scores, neonatal asphyxia, and NICU admission. Sensitivity analysis (SA) used multivariable regression adjusting for residual imbalances in gravidity, parity, premature rupture of membranes, and hypertensive disorders. Results PSM successfully matched 87 cases (29 vaginal, 58 cesarean). After matching, most covariates achieved SMD < 0.10. The PPH rate was higher in the vaginal delivery group than in the cesarean group (44.8% vs. 1.7%; OR 46.31, 95% CI 5.63–381.30, P < 0.001), and the 5-min Apgar score was lower in the vaginal delivery group (β = −0.40, 95% CI − 0.66 to − 0.14, P = 0.003). Sensitivity analysis confirmed the robustness of these findings. No significant differences were observed in hospital stay, MICU admission, birth weight, macrosomia, neonatal asphyxia, or NICU admission. Conclusions In women with class III obesity (BMI ≥ 40 kg/m²), vaginal delivery was associated with a substantially increased risk of postpartum hemorrhage. After carefully weighing maternal and neonatal benefits and risks, planned cesarean delivery may be considered one of several clinical options; multicenter validation is warranted.