The objective of this study was to compare the risk factors and peripartum outcomes among patients who had nonelective cesarean delivery with umbilical arterial pH < versus > or = 7.00. A case-control study of parturients who delivered by nonelective cesarean delivery and had a neonate with a pH < 7.00 were compared with the next four patients who delivered abdominally but had a newborn with a normal pH. Among 45 newborns with pH < 7.00 the rate of cesarean delivery for nonreassuring fetal heart rate was significantly more common in the case (56%) than control group (16%). The rates of end organ failure and neonatal death were similar for both groups. Although newborns with pH < 7.00 were significantly more likely to have cesarean delivery for nonreassuring fetal heart rate patterns and be admitted to the neonatal intensive care unit, there was no means to identify these patients until the abnormalities in tracing developed.