Effect of Smoking on Serum Concentrations of Total Homocysteine, Folate, Vitamin B12, and Nitric Oxide in Pregnancy: A Preliminary Study

Abstract

Objective: Nitric oxide (NO) is a potent vasodilator released by endothelial cells that plays an important role in modulating maternal and fetal vascular tone in normal pregnancy. Lower plasma levels of vitamins may result in hyperhomocysteinemia, a known risk factor in pregnancy. The aim of this study was to investigate whether there are alterations in the serum levels of total homocysteine (tHcy), folate, vitamin B₁₂, and total nitrite, as an index of NO, in smoking as compared with age-matched nonsmoking pregnant women. Methods: Thirty-three women (19 smoking and 14 nonsmoking) between 16 and 22 weeks of their gestation were included in this study. The serum tHcy levels were analyzed by using an enzyme-linked immunosorbent assay kit. Vitamin B₁₂ and folate values were measured by means of DPC kits. Total nitrite was measured by Griess reaction as an index of endogenous NO production. Results: The serum tHcy concentrations were significantly increased in smoking as compared with nonsmoking pregnant women (p < 0.001). The folate and vitamin B₁₂ concentrations were lower in smoking than in nonsmoking pregnant women, but only the differences in folate concentrations were statistically significant (p < 0.001). The tHcy concentrations showed a significant negative correlation with folate in the smoking pregnant women. The serum total nitrite concentrations were lower in smoking than in nonsmoking pregnant women (p < 0.05). In addition, the serum nitrite levels in smoking pregnant women had significant negative correlations with tHcy and positive correlations with folate and vitamin B₁₂ levels. Conclusions: In the light of our findings, we propose that smoking might enhance the vasoconstrictor capacity in pregnant women by increased tHcy concentrations and by a simultaneous decrease in the production of NO which is a vasodilator compound.