Aim: We measured umbilical cord blood and maternal plasma concentrations of labetalol hydrochloride (labetalol) at delivery in women with pregnancy induced hypertension (PIH) who received labetalol treatment, and also investigated the influence of labetalol on neonatal findings.
Methods: We surveyed background, neonatal findings, and health checkups after birth among PIH patients who received labetalol. Umbilical cord blood was collected within 15 min after delivery and venous blood within 2 h. Umbilical cord blood and maternal plasma concentrations of labetalol were measured using liquid chromatography-tandem mass spectrometry.
Results: PIH was evaluated as severe hypertension in 20 patients and mild hypertension in 9 according to the Guidelines for the Management of PIH. Umbilical cord blood concentrations of labetalol were 17.2±11.4 ng/ml in the 150 mg/day group (n=22) and 32.8±11.6 ng/ml in the 300 mg/day group (n=7). Mean maternal plasma concentrations of labetalol in the 150 mg/day and 300 mg/day groups were 29.2±21.0 ng/ml and 49.3±12.6 ng/ml, respectively. The 300 mg/day group also included 2 low-birthweight neonates, whose Apgar scores were 5 after 1 min but returned to normal values after 5 min. There were no abnormalities in Apgar score or umbilical cord blood pH in any other neonates and no abnormal findings at neonatal checkups. Patients who continued drug therapy after delivery even performed breast feeding.
Conclusions: There was some correlation between labetalol concentrations in umbilical cord blood and in maternal plasma (r=0.688), with the former corresponding to 60% to 70% of the latter.