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

OBJECTIVE: The purpose of this study was to characterize the effect of smoking on the incidence of various pregnancy complications.

STUDY DESIGN: 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.

RESULTS: 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).

CONCLUSION: 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.