Smoking in pregnancy revisited: findings from a large population-based study.

Abstract

The purpose of this study was to characterize the effect of smoking on the incidence of various pregnancy complications. A population-based retrospective analysis with a perinatal database of 170,254 singleton pregnancies was performed. The rate of pregnancy complications was calculated in 4 strata of smokers: Nonsmokers, 1 to 5 cigarettes per day, 6 to 10 cigarettes per day, and >10 cigarettes per day. Logistic regression was used to calculate odds ratios as measures of an association of smoking with various pregnancy complications after correction for confounding factors. The mean age of the study population was 29 +/- 4.8 years. The odds ratio for preeclampsia was 0.64 (95 % CI, 0.59-0.70), for intrauterine growth restriction was 2.4 (95% CI, 2.34-2.53), and for preterm delivery was 1.2 (95% CI, 1.13-1.28). Smoking decreased the incidence of preeclampsia in a dose-effect manner and was shown to increase the rate of intrauterine growth restriction and preterm delivery.