Objective: We sought to investigate maternal and fetal nitroglycerin metabolization and to assess the clinical condition of neonates after intravenous nitroglycerin application during cesarean delivery. Study Design: At the time of the uterine puncture incision, either 0.25 mg or 0.5 mg nitroglycerin or a physiologic sodium chloride solution was administered as an intravenous bolus. Plasma concentrations of nitroglycerin and its metabolites were measured in maternal venous blood and in umbilical blood samples taken immediately after cord clamping. Arterial blood pressure, pulse rates, and Apgar scores were recorded for the neonates 1, 5, and 10 minutes after birth. Results: Sixty-two patients were included in the pharmacokinetic study. Median maternal plasma levels 1 and 5 minutes after injection of 0.5 mg nitroglycerin were 80 and 3.2 ng/mL, respectively; median maternal plasma levels 1 and 5 minutes after injection of 0.25 mg nitroglycerin were 38 and 1.2 ng/mL, respectively. In the umbilical vein 1 minute after application of 0.5 mg or 0.25 mg nitroglycerin, the plasma levels were 0.41 and 0.09 ng/mL, respectively, and in the umbilical artery they were 0.03 and 0.008 ng/mL, respectively. Circulatory parameters and Apgar scores in the neonates did not differ significantly from those found in the placebo group. Conclusion: The level of nitroglycerin in umbilical plasma was two to three orders of magnitude lower than that found in maternal plasma and clearly in a subtherapeutic range. There was no indication that prenatal application of nitroglycerin to facilitate obstetric management is hazardous for neonates. (Am J Obstet Gynecol 2000;182:955-61.)