Objective
This study aimed to investigate the endothelium-dependent relaxation of uterine small arteries from pregnant nonsmokers, smokers, and ex-smokers who stopped smoking early in pregnancy.

Study Design
Uterine arteries were dissected from myometrial biopsies obtained during elective cesarean sections of 34 uncomplicated, singleton pregnancies, and the vascular function was assessed in a wire myograph for isometric recordings. Serum cotinine verified self-reported smoking; 15 were nonsmokers, 10 were smokers, and 9 were ex-smokers.

Results
Arteries from smokers and ex-smokers had reduced bradykinin-induced relaxation compared to arteries from nonsmokers (P < .05). The relaxation response to the nitric oxide donor sodium nitroprusside was similar in arteries from nonsmokers and smokers but was better in arteries from ex-smokers (P < .05).

Conclusion
The findings suggest that maternal smoking reduces endothelium-dependent nitric oxide–mediated relaxation in uterine small arteries and that smoking cessation early in pregnancy does not fully abolish this deleterious effect, despite improvement in relaxation to nitroprusside.