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Lumbar epiduval analgesia with bupivacaine was given to 37 women for uncomplicated labor. After the blcokade serial determinations of pH and bupivacaine concentration were made in fetal scalp blood and maternal venous blood and there was continuous monitoring of the fetal heart rate. Fetal scalp blood pH was within normal limits and no pathologic FHR tracings were elicited by the blockade, although a temporary decrease of the baseline fetal heart rate irregularity was seen in about one-fifth of the cases. Fetal drug concentrations were low and about one-fourth of corresponding maternal values. After reinjection of bupivacaine the degree of drug accumulation was fairly similar in fetal and maternal blood.

Lumbar epidural analgesia with bupivacaine was administered to 33 women for relief of pain during labor. At delivery blood samples were drawn from the umbilical cord vessels and from a maternal peripheral vein. Blood samples were also collected from the noenate and its mother, 1, 4, and 20 hours after delivery. Analyses of bupivaccaine concentrations were carried out in all samples with a gas-chromatographic technique. The drug concentration in the umbilical vein (UV) was usually higher than the corresponding umbilical artery value (UA), but with increasing time interval between the last bupivaccaine infection and delivery the UA/UV drug concentration ratio rose. After delivery the rate of drug decline in blood was similar in mother and newborn infant. The clinical condition of the infant was unrelated to the drug concentration in the umbilical cord vessels.