Association between neonatal birthweight and maternal vaginal wall prolapse: a retrospective analysis of postpartum women

Objective To investigate the association between neonatal birthweight (BW) and the maternal risk of anterior and posterior vaginal wall prolapse in the postpartum period. Methods This retrospective cross-sectional study included 864 postpartum women undergoing routine follow-ups after delivery. Participants were categorized into quartiles according to BW. Multivariate logistic regression models were applied to evaluate the association between BW and moderate-to-severe vaginal wall prolapse [Pelvic Organ Prolapse Quantification (POP-Q), POP-Q stage ≥ II], sequentially adjusting for maternal age, parity, mode of delivery, and plurality. Restricted cubic spline (RCS) analyses were used to examine potential non-linear relationships, accompanied by subgroup and sensitivity analyses. Results In the fully adjusted model, each 1 kg increase in BW was associated with a 71% higher risk of posterior vaginal wall prolapse (OR = 1.71, 95% CI: 1.18–2.53, P = 0.006), whereas the overall association with the anterior wall was not significant (OR = 1.35, 95% CI: 0.93–1.98, P = 0.125). In the quartile analysis, women in the highest BW group (≥3.415 kg) had a 2.26-fold higher risk of posterior wall prolapse ( P for trend < 0.001). In comparison, a significant increase in risk was also observed for the anterior wall in the moderate BW group (3.15–3.415 kg) (OR = 1.62, 95% CI: 1.02–2.61). RCS analysis revealed non-linear dose–response relationships between BW and anterior and posterior wall prolapse, with inflection points around 3.2 kg and 3.7 kg, respectively. The risk increase was more pronounced in the lower BW range (< inflection point), and delivery mode acted as a significant effect modifier. Conclusion Higher BW is an independent risk factor for maternal posterior vaginal wall prolapse, showing both dose-dependent and threshold effects. The results suggest that women who deliver larger babies may require enhanced postpartum pelvic floor evaluation and follow-up management, and further prospective studies are needed to explore the long-term implications of these findings on pelvic floor health.