Comparison of external cephalic version outcomes among pregnant women with different gestational weight gains under combined neuraxial analgesia and tocolysis: a retrospective study

External cephalic version (ECV) is an established method for reducing cesarean section rates in fetal malpresentation. While gestational weight gain (GWG) may influence ECV success, evidence remains limited. We evaluated the impact of GWG patterns on ECV success rates under combined neuraxial analgesia and tocolysis. We included pregnant women undergoing ECV with neuraxial analgesia and tocolysis at Fudan University Obstetrics and Gynecology Hospital (2018–2024). Participants were classified according to 2021 Chinese Nutrition Society (CNS) guidelines as having below-target, within-target, or above-target GWG. Primary outcome was ECV success rate. Multivariate logistic regression assessed the association between GWG and success, adjusting for maternal factors. Among 319 eligible cases, ECV success rates varied across GWG categories: 87.7% (below-target), 72.2% (within-target), and 64.8% (above-target) (p = 0.029). After adjustment for confounders, both within-target GWG (adjusted OR 0.304, 95% CI 0.099–0.938, p = 0.044) and above-target GWG (adjusted OR 0.250, 95% CI 0.087–0.719, p = 0.019) demonstrated significantly reduced ECV success compared to below-target GWG. Non-anterior placental position (adjusted OR 1.908, 95% CI 1.134–3.201, p = 0.014) and higher amniotic fluid index (AFI) (adjusted OR 1.009 per mm increase, 95% CI 1.001–1.017, p = 0.018) were positively associated with ECV success. Pregnant women with below-target GWG showed significantly higher ECV success rates under combined neuraxial analgesia and tocolysis. Non-anterior placental position and higher AFI were additionally associated with procedural success. These findings may optimize patient selection and enhance pre-procedure counselling for ECV attempts. The clinical trial registration number is ChiCTR2500098423/ https://www.chictr.org.cn/showproj.html? proj=258486 Date of registration 03/7/2025.