Association of obesity with outcomes of attempted operative vaginal delivery

To assess whether outcomes of attempted operative vaginal delivery (OVD) are associated with obesity among nulliparous individuals. This is a secondary analysis from the prospective cohort Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-To-Be study. This analysis included participants with cephalic liveborn non-anomalous singletons who delivered ≥34 weeks of gestation and had attempted OVD. The primary exposure was maternal obesity defined by body mass index (BMI) at delivery (obese: BMI ≥30 kg/m2 vs. non-obese: BMI < 30 kg/m2 [referent]). The primary outcome was failed OVD, defined as a cesarean delivery following attempted OVD, and secondarily maternal and neonatal adverse outcomes. Multivariable logistic regression was used to adjust for covariates, and statistical interaction between BMI and instrument type (forceps or vacuum) was assessed. When the interaction was significant, stratified analyses were performed and presented. Of 10,038 individuals in the parent study, 791 (7.9%) had an attempted OVD and were included in the analysis. 325 (41%) had BMI ≥30 at delivery. The type of instrument used was no different based on obesity status. Failed OVD, which occurred in 6.8% of attempts, was more frequent in those with obesity (10.1 vs 4.2%; p=0.005; aOR 2.23, 1.16-4.28), with no significant interaction by instrument type (Table 1). There was an interaction (p=0.046) between composite neonatal morbidity and instrument type. Stratified analysis revealed that composite neonatal morbidity was more likely following attempted vacuum in infants of people with obesity (32.7 vs 22.3%, aOR 1.61, 1.07-2.43) but not following forceps attempt. Other adverse outcomes were neither different by obesity status nor had significant interactions with instrument type (Table 2). Among nulliparas, attempted OVD was more likely to fail in people with obesity. Neonates of people with obesity who underwent attempted vacuum, but not attempted forceps, had higher composite morbidity than those with BMI < 30.View Large Image Figure ViewerDownload Hi-res image Download (PPT)