500 Obesity is associated with increased rates of umbilical artery pH< 7.1 at scheduled cesarean delivery

Limited data suggest obese women are at increased risk for decreased fetal umbilical artery (UA) pH prior to the onset of labor. Reduction in venous return from the weight of the abdominal wall and a decrease in maternal blood pressure in response to neuraxial anesthesia may contribute to hypoperfusion leading to a decreased UA pH. We hypothesize that obese women are at increased risk for UA pH <7.1 at time of non-labor cesarean delivery (CD) under neuraxial anesthesia. This multi-center retrospective cohort includes women who delivered a term, singleton, non-anomalous neonate from 2013-2019 via non-labor CD under neuraxial anesthesia. Multiple gestations and patients with suspected fetal growth restriction were excluded. Universal cord gas collection was routinely performed. Primary outcome was fetal UA pH <7.1 and base deficit ≥12 mmol in obese vs. non-obese gravidas. Secondary outcomes included NICU admission and other neonatal morbidities. Outcomes were assessed using multivariable logistic or linear regression and adjusted for age, race/ethnicity, insurance type, number of prior CDs, maternal medical problems, time from anesthesia placement to delivery and time from skin incision to delivery. Obesity was associated with younger maternal age, longer time from anesthesia placement and skin incision to delivery, non-White race, public insurance, higher order CD, tobacco use, hypertensive disorders and diabetes (all p<0.01). Obese patients were significantly more likely to have UA pH <7.1 (aOR 2.4, 95% CI 1.5-3.6; p<0.01) and UA base deficit ≥12 mmol (aOR 3.1, 95% CI 1.5-3.6; p<0.01). There was a significant trend toward UA pH <7.1 and base deficit ≥12 mmol with increasing class of obesity. We found no differences in secondary outcomes between groups. Maternal obesity is associated with increased rates of UA pH <7.1 and base deficit ≥12 mmol at time of non-labor CD under neuraxial anesthesia. These findings may prompt alterations in management of the obese parturient and may alter prediction of adverse outcomes in the neonate by fetal cord blood gas results.View Large Image Figure ViewerDownload Hi-res image Download (PPT)