This study aimed to investigate the effect of maternal cigarette smoking on endothelial nitric oxide synthase (eNOS) activity and concentration in the fetal umbilical vein, and subsequently, to relate the findings to the size of the newborn.

Forty-four nonsmoking and 30 smoking women were included in the study. Umbilical vein endothelial cells were isolated immediately after delivery. The eNOS activity was determined in the samples by the conversion of ¹⁴C-l-arginine to ¹⁴C-l-citrulline, and the eNOS concentration was determined by a human eNOS immunoassay.

Newborns of smokers had a lower weight (P=.014) and a smaller head circumference (P=.002) than those newborns of nonsmokers. The eNOS activity in fetal umbilical veins exposed to maternal smoking was 40% lower (P=.006), and the eNOS concentration 32% lower (P=.053) in newborns of smokers than in nonsmokers.

The findings suggest that maternal smoking reduces nitric oxide production in the fetal circulation. This may contribute to retarded fetal growth caused by the subsequent endothelial dysfunction with reduction of dilatory capacity of the vessels.