Maternal and neonatal fentanyl and bupivacaine concentrations after epidural infusion during labor.

Labor analgesia using continuous epidural infusions of low-dose bupivacaine and fentanyl may be maintained for many hours. We examined the potential for drug accumulation in both mother and neonate after these long-term infusions. Pregnant women receiving a 10-mL/h continuous infusion of labor analgesia with 0.125% bupivacaine and 2 micrograms/mL of fentanyl were evaluated. Maternal venous and umbilical venous drug concentrations were measured at delivery. Umbilical artery blood gases were obtained. Scanlon neurobehavioral testing was performed on all infants. Length of infusion times varied from 1 to 15 h. Maternal and neonatal drug concentrations remained relatively constant throughout the infusion period. All umbilical blood gas values and neurobehavioral scores were within normal limits. In conclusion, even when maintained for many hours, continuous infusion labor analgesia does not appear to result in significant fetal drug accumulation. No adverse neonatal effects were seen.