The effect of cigarette smoking during pregnancy on mode of delivery in uncomplicated term singleton pregnancies

Objective: To examine the influence of cigarette smoking during pregnancy on mode of delivery. Methods: A retrospective analysis of 6105 uncomplicated term singleton pregnancies for mode of delivery was performed with respect to smoking status. Results: Of all, 680 (84.0%) smokers and 4588 (86.7%) non-smokers had a spontaneous vaginal delivery, 65 (8.0%) smokers and 393 (7.4%) non-smokers had an instrumental delivery and 65 (8.0%) smokers and 314 (5.9%) non-smokers had a cesarean delivery (p=0.051). Smoking during pregnancy increased the risk of any operative or instrumental intervention by OR 1.240, 95% CI 1.012-1.523. Non-reassuring fetal heart rate pattern that warranted either cesarean or instrumental intervention was present in 99 (12.2%) out of 810 smokers and in 392 out of 5295 (7.4%) non-smokers, p<0.001). Smoking during pregnancy increased the risk of non-reassuring fetal heart rate pattern that warranted either cesarean or instrumental intervention by OR 1.650 (95% CI 1.341-2.022). Conclusion: Women with uncomplicated term singleton pregnancies who smoke during pregnancy are at an increased risk of fetal compromise during labor (as judged by non-reassuring fetal heart rate pattern), leading to increased rates of operative delivery (cesarean either instrumental).