(846) Prolonged second stage: How does obesity influence likelihood of successful vaginal delivery?

In 2024, ACOG revised clinical guidelines supporting the definition of a prolonged second stage labor as ≥ 3 hours. We sought to evaluate the difference in vaginal delivery rate for nulliparous patients with a singleton, term, vertex fetus (NTSV) with prolonged second stage between those with and without obesity. 



Study Design:

A retrospective cohort study of NTSV patients with a prolonged second stage of labor (≥ 3 hours) delivered at a single tertiary care hospital from 6/1/2023-12/31/2023. Obesity was defined as body mass index (BMI) >30 kg/m² at delivery. The primary outcome was vaginal delivery and secondary outcomes were select maternal and neonatal morbidities. Categorical variables were compared using Chi square, Fisher’s exact and normally distributed continuous variables using Student’s T test, as appropriate. Multivariable logistic regression was used to adjust for confounders. 



Results:

173 patients with a prolonged second stage were included, 99 (57.2%) without obesity and 74 (42.8%) with obesity. Patients with obesity were more likely to have hypertension (p=0.04) and hypertensive disorders of pregnancy (p=0.02), as well as utilize oxytocin in the second stage (p=0.04). 94 (94.9%) patients without obesity achieved a vaginal delivery compared to 62 (83.8%) with obesity (RR 0.88, 95% CI 0.67-0.98). After adjusting for confounders and compared to patients without obesity, patients with obesity were noted to have an adjusted relative risk of 0.81 (95% CI 0.54-0.96) for vaginal delivery. There was no difference between the groups with regard to operative vaginal delivery and maternal and neonatal morbidities. These findings persisted after adjusting for confounders. 



Conclusion:

While patients with obesity had a lower likelihood of vaginal delivery after a prolonged second stage compared to patients without obesity, both groups were overall highly successful in delivering vaginally and no differences in likelihood for select maternal or neonatal complications occurred. These findings may aid in counseling patients with a prolonged second stage.