The effects of maternally administered pethidine or epidural bupivacaine on the fetus and newborn.
The continuous fetal heart rate rate pattern, condition of the baby at birth and its subsequent behaviour were compared in three groups of infants whose mothers received during labour either no drugs, intramuscular pethidine or epidural bupivacaine. The blood levels of pethidine and bupivacaine were measured at delivery in a maternal vein, and umbilical artery and vein, and in the newborn during the first 48 hours of life. The only significant changes in the fetal heart rate pattern occurred in association with maternal hypotension or uterine hyperstimulation. The Apgar scores at one minutes were 7 or less in more infants in the intramuscular pethidine and epidural bupivacaine groups as compared with the controls. There were no differences in the Apgar scores at five minutes. Neonatal behaviour during the first six weeks of life was not significantly affected by pethidine or epidural bupivacaine when compared with the control group. Pethidine and bupivacaine were shown to cross the placenta freely. The half-life of these drugs in the newborn was longer than in the adult.