411: Effects of labor on metabolic indicators of fetal stress in newborns delivered via cesarean section

Abstract

High concentrations of umbilical artery (UA) lactate have been associated with poor neonatal outcomes, including acidosis, hypoxic-ischemic encephalopathy, among others. We sought to determine the effect of labor on the metabolic profiles, namely UA pH, lactate and base excess, of neonates who were delivered via Cesarean section. In this prospective cohort study, UA cord blood samples were collected from singleton cesarean deliveries between June and August 2019 at a tertiary care center. UA pH, lactate and base excess were then assessed using a GEM 4000 blood gas analyzer. Maternal labor course and urgency of delivery were determined from medical records. Statistical analyses, namely two-sample T-tests, were performed using StatPlus software. 88 cesarean sections were included in the study. 27 of these deliveries were out of labor while 61 of the women did not labor prior to undergoing cesarean section. The mean UA pH was lower in samples where mothers had previously labored (7.20 vs. 7.25 in the non-laboring group, p=0.003). UA lactate was also significantly higher in the out of labor group (5.01 mmol/L) than in the non-laboring group (3.24 mmol/L, p=0.00002). Lastly, mean UA base deficit was significantly lower in the out of labor group (-6.54) when compared to the non-laboring group (-4.06, p=0.0002). These differences persisted when accounting for the urgency of delivery (STAT vs. non-STAT cesarean section). Our data supports the intuitive idea that labor results in a degree of metabolic stress to the fetus, which may impact buffering capacity and predispose the neonate to injury if unheeded. More data is needed to further describe the relationship between the length of labor and neonatal metabolic status, as well as possible implications for neonatal wellbeing.