(563) Second stage of labor duration among patients with obesity: How likely is vaginal delivery?

Objective: ACOG recently revised guidelines defining an abnormally prolonged second stage labor as ≥ 3 hours. We sought to evaluate the difference in vaginal delivery rate for nulliparous patients with obesity and a singleton, term, vertex fetus (NTSV) with a normal (< 3 hour) versus prolonged (≥ 3 hour) second stage of labor.

Study Design: A retrospective cohort study of NTSV patients with obesity who achieved the second stage of labor, delivered at a tertiary care center hospital from 6/1/2023-12/31/2023. Obesity was defined as BMI ≥ 30 kg/m² on admission. The primary outcome was vaginal delivery. Secondary outcomes included select maternal and neonatal morbidities. Categorical variables were compared using Chi square and Fisher's exact. Normally distributed continuous variables were assessed using Student’s T-test. Multivariable logistic regression was used to adjust for confounders.




Results: Of 348 included patients, 274 (78.7%) had a second stage < 3 hours and 74 (21.3%) had a second stage ≥ 3 hours. Those with a prolonged second stage were older (p=0.04), more likely to be admitted for induction of labor (p< 0.01) and utilize oxytocin in the second stage (p=0.02). After adjusting for confounders, a prolonged second stage was associated with a 22% lower likelihood of vaginal delivery (aRR 0.78, CI 0.41-0.95). Patients with a prolonged second stage were more than 4 times as likely to have an operative vaginal delivery (aRR 4.54, 95% CI 2.97-6.29). 3^rd degree lacerations were more likely in a prolonged second stage (aRR 10.25, 95% CI 2.02-41.55); however, the overall frequency was low. There were no other differences in maternal or neonatal morbidities between the groups.



Conclusion: While NTSV patients with obesity and a prolonged second stage of labor had a lower likelihood for vaginal delivery compared to those with a normal second stage duration, both groups had high rates of success. In patients with a prolonged second stage, 40% had an operative vaginal delivery, highlighting the importance of this obstetric skill in preventing the first cesarean section in patients with a protracted labor course.