Risk factors for fetal acidemia at time of scheduled cesarean delivery

Abstract

While fetal acidemia is most commonly detected after labor or in the setting of non-reassuring fetal status, it can also be seen in the setting of scheduled prelabor cesareans. We identified risk factors for unexpected acidemia at time of scheduled cesarean. This was a nested case-control study of all women delivering live, non-anomalous neonates via scheduled cesarean ≥ 37 weeks gestation from 2004-2014 at a single tertiary care center with a universal cord gas policy. Women with onset of labor prior to cesarean or cesarean performed for non-reassuring fetal status were excluded from this study. The primary outcome was the incidence of fetal acidemia (umbilical artery [UA] pH < 7.20). Bivariate analysis was conducted to identify maternal and fetal factors associated with acidemia. Multivariable logistic regression was used to adjust for confounders. Of 2081 pregnancies meeting inclusion criteria, 252 (12.1%) were complicated by fetal acidemia. In the bivariate analysis, breech presentation, macrosomia, gestational diabetes, and obesity were associated with acidemia (Table). In the multivariable regression model, obesity and breech presentation were the only remaining risk factors associated with acidemia after adjusting for confounding (Figure). There was a dose-dependent increase in odds of acidemia as BMI increased, with class 3 obesity (BMI > 40 kg/m2) conferring 3-fold increased odds of acidemia compared to non-obese women (aOR 3.00, 95% CI 2.01-4.47). In a secondary analysis using pH < 7.10 as the outcome, Class 3 obesity was the only significant risk factor (aOR 3.14, 95% CI 1.66-5.95). Maternal obesity and breech presentation confer an increased risk of fetal acidemia at the time of scheduled cesarean section, even in the setting of reassuring monitoring prior to delivery. Further research is needed to identify if any additional operative factors such as maternal hypotension or increased operative time may explain the increased odds of acidemia in these at-risk patients.View Large Image Figure ViewerDownload Hi-res image Download (PPT)