Association Between Obesity and Fetal Acidosis at Scheduled Cesarean Delivery

To evaluate whether patients with obesity who undergo scheduled cesarean delivery under neuraxial anesthesia are at increased risk for umbilical artery pH less than 7.1 and base deficit 12 mmol or greater.

We conducted a multicenter, retrospective cohort study of individuals who delivered a term, singleton, nonanomalous neonate at one of four academic medical centers in New York City from 2013 to 2019 by scheduled cesarean under neuraxial anesthesia for whom fetal cord blood gas results were available. The primary study outcome was rate of fetal acidosis , defined as umbilical artery pH less than 7.1. This was compared between patients with obesity (body mass index [BMI] 30 or higher) and those without obesity (BMI lower than 30). Base deficit 12 mmol or greater and a composite of fetal acidosis and base deficit 12 mmol or greater were also compared. Secondary outcomes included neonatal intensive care unit admission rate, 5-minute Apgar score less than 7, and neonatal morbidity. Associations between maternal BMI and study outcomes were assessed using multivariable logistic or linear regression and adjusted for age, race and ethnicity, insurance type, cesarean delivery order number, and neuraxial anesthesia type.

Of the 6,264 individuals who met inclusion criteria during the study interval, 3,098 had obesity and 3,166 did not. The overall rate of umbilical artery cord pH less than 7.1 was 2.5%, and the overall rate of umbilical artery base deficit 12 mmol or greater was 1.5%. Patients with obesity were more likely to have umbilical artery cord pH less than 7.1 (adjusted odds ratio [aOR] 2.7, 95% CI 1.8-4.2) and umbilical artery base deficit 12 mmol or greater (aOR 3.2, 95% CI 1.9-5.3). This association was not significantly attenuated after additional adjustments for potential mediators, including maternal medical comorbidities. We found no differences in secondary outcomes between groups.

Maternal obesity is associated with increased odds of arterial pH less than 7.1 and base deficit 12 mmol or greater at the time of scheduled cesarean delivery under neuraxial anesthesia.