556: Contributors to neonatal acidemia among morbidly obese gravidas at term cesarean delivery

Abstract

Neonatal acidemia after scheduled cesarean delivery has been reported with greater frequency in obese gravidas. Uterine hypoperfusion from relative hypotension, visceral adipose tissue compression, pannus retraction with pfannenstiel incisions, retractor use, and prolonged operative times have been implicated. We aimed to evaluate intraoperative factors that contribute to neonatal acidemia during scheduled cesarean delivery. We conducted a retrospective cohort study of all nonanomalous singleton pregnancies delivering via scheduled cesarean under spinal anesthesia between 5/2009-1/2017 at our academic tertiary care center.The primary outcome was the incidence of an umbilical arterial cord pH< 7.1. 596 deliveries met study criteria and were included for analysis. Groups were similar in maternal age, ethnicity, insurance, and gestational age. The incidence of an umbilical pH< 7.10 in the cohort was 4% (24/596). Mothers of acidemic infants had mean BMI of 43±13 kg/m2 vs. 35±10 kg/m2 in mothers of non-acidemic infants. 42% (10/24) of infants with pH< 7.1 were admitted to NICU vs. 15% (88/571) with pH ≥ 7.1 (p=.002). Median birth weight was higher among acidemic infants (3692 ± 850g vs. 3294 ± 660g, p=.004) and maternal diabetes was more frequent [46%(11/24) vs. 15%(88/572), p<.001). As maternal BMI increased, so did operative times, intraoperative hypotension (max drop systolic blood pressure, SBP), retractor use, non-pfannenstiel incisions, maternal diabetes, and birthweight. (Table). Mean vasopressor doses were similar among BMI groups as was NICU admission. In a logistic regression model, the factors of BMI (AOR 1.07, 95%CI 1.03-1.12, p=.002), maternal diabetes (AOR 3.65, 95%CI 1.45-9.18, p=.006), and ephedrine dose (AOR 1.06, 95%CI 1.03-1.09, p<.0001), were found to be predictive of umbilical artery pH< 7.1, while maximum drop in SBP, maternal age, phenylephrine dose, incision type, and retractor use were not predictive. Neonatal arterial pH < 7.1 at time of scheduled cesarean delivery was associated with maternal obesity, diabetes, and ephedrine dose but not intraoperative hypotension, retractor use, or incision type. Further studies are needed to determine the role of external uterine compression and anesthesia-associated maternal hypotension to the increased rates of neonatal acidemia seen in obese gravidas.