215: Risk factors for fetal acidemia at time of scheduled cesarean delivery

Abstract

Fetal acidemia is associated with serious long-term sequelae, including cerebral palsy, hypoxic-ischemic encephalopathy, and death. While fetal acidemia is most often encountered after labor, it is also occasionally seen in the setting of prelabor cesarean. We aimed to estimate the incidence of fetal acidemia in women undergoing planned cesarean delivery and to identify maternal risk factors associated with fetal acidemia. This retrospective cohort study evaluated all women delivering live, non-anomalous neonates via scheduled cesarean at or beyond 37 weeks gestation from 2004 to 2014 at a single, academic tertiary care center with a universal cord gas policy. Women with multifetal gestations or onset of labor prior to cesarean were excluded from this study. Paired umbilical cord gases were collected immediately after delivery. The primary outcome was the incidence of fetal acidemia (umbilical artery pH ≤ 7.1). Univariate analysis was conducted to identify maternal and operative factors associated with acidemia. Multivariable logistic regression was used to adjust for confounders. Of 3,005 pregnancies meeting inclusion criteria, 121 (4.0%, 95% CI 3.3%-4.7%) were complicated by fetal acidemia. After controlling for confounders, hypertension, diabetes, incision to delivery time, prior cesarean, advanced maternal age, and macrosomia (birth weight ≥ 4000g) were not associated with acidemia. Caucasian race was protective (aRR 0.61, 95% CI 0.38-0.97) against acidemia, while maternal obesity (BMI ≥ 30 kg/m2) was a significant risk factor for fetal acidemia (aRR 1.70, 95% CI 1.10-2.62). Notably, there was a dose-dependent relationship between increasing maternal BMI and incidence of fetal acidemia, with super morbidly obese women (BMI ≥ 50 kg/m2) having a five-fold increased risk of fetal acidemia (13.2% v 2.6%, aRR 4.97, 95% CI 2.71-9.14; Table). Maternal obesity is the only modifiable risk factor for fetal acidemia identified in this cohort of women undergoing prelabor cesarean, with a significant dose-dependent relationship between increasing maternal BMI and incidence of fetal acidemia. Future studies should investigate potential etiologies for this finding and evaluate the short- and long-term impact of acidemia in infants born to obese women.