(666) Maternal body mass index, maneuvers, and neonatal morbidity associated with shoulder dystocia

To compare the frequency and type of maneuvers used to resolve social dystocia (SD) by maternal pre-pregnancy body mass index (BMI) and the association between BMI and neonatal adverse outcomes following SD.

Study Design: We conducted a retrospective cohort study of pregnant individuals who experienced an SD at delivery from June 2012-July 2021 at a tertiary care center.  We included singleton nonanomalous livebirths ≥36 weeks’ gestation. The primary exposure was pre-pregnancy BMI categorized as: < 30 kg/m², 30-34.9- kg/m², and ≥35 kg/m². The composite neonatal outcome included neonatal injury, seizures, hypoxic ischemic encephalopathy, 5-minute APGAR < 7, and secondarily, NICU admission and neonatal acidemia (pH < 7.10). SD duration and number and types of maneuvers were compared by BMI groups. Multivariable logistic regression was used and adjusted for diabetes in pregnancy, operative vaginal delivery, and nulliparity.

Results:

Among 883 individuals who experienced an SD at delivery, 608 (68.9%) had a BMI < 30, 161 (18.2%) were BMI 30-34.9, and 114 (12.9%) were BMI ≥35. The median duration of SD was 40 (IQR 30, 60) seconds and did not vary by maternal BMI. Deliveries complicated by BMI ≥35 were more likely to require ≥3 maneuvers compared to those with non-obese BMI (aOR 2.06, 95% CI 1.33-3.19). Suprapubic pressure (90.0%) and delivery of the posterior arm (40.9%) were the most commonly used maneuvers in all groups. Rubin’s and delivery of the posterior arm maneuvers were more commonly used in the BMI ≥35 group compared to BMI <  30 (RR 1.49, 95% CI 1.11-2.01; RR 1.32, 95% CI 1.08-1.61, respectively) categories. Composite neonatal adverse outcomes did not differ by BMI, but neonatal injury was more common in those with BMI ≥35 (aOR 2.03, 95% CI 1.11-3.75). Interaction between BMI category and number of maneuvers was not significant (p=0.09).  

Conclusion:

Among pregnant individuals who experienced a SD, increased pre-pregnancy BMI was associated with increased number of maneuvers performed during a SD, but not its duration. Risk of neonatal injury following SD is higher if maternal BMI is ≥35 kg/m².