Maternal cigarette smoking and the risk of pregnancy-induced hypertension and eclampsia.

Background Although previous studies have found that maternal smoking decreases the risk of pregnancy-induced hypertension (PIH), the difference of this effect between primiparous and multiparous women has not been well studied and the results of the exposure–response relationships between maternal smoking and PIH are inconsistent. No previous study has specifically examined the relationship between maternal smoking and eclampsia.Methods We analysed data from a population-based retrospective cohort study of 3 153 944 singleton pregnancies in the US. The data were derived from the national linked birth/infant mortality database for 1998. Multiple logistic regressions were used to describe the relationship between cigarette smoking and PIH and eclampsia.Results The adjusted odds ratios (ORs) [95% confidence intervals (95% CIs)] for PIH were 0.80 (0.77–0.83) for primiparous women and 0.81 (0.78–0.83) for multiparous women among smokers compared with non-smokers. The corresponding adjusted ORs (95% CIs) for eclampsia were 0.74 (0.66–0.82) and 0.75 (0.68–0.83), respectively. For PIH, the adjusted OR (95% CI) for smokers vs non-smokers were 0.82 (0.79–0.86), 0.81 (0.78–0.83), 0.80 (0.77–0.83), and 0.88 (0.79–0.98), respectively, for 1–5, 6–10, 11–20, and >20 cigarettes per day (test for trend: P = 0.86). The corresponding figures for eclampsia were 0.85 (0.75–0.95), 0.74 (0.66–0.82), 0.68 (0.58–0.78), and 0.73 (0.49–1.04), respectively (test for trend: P = 0.02).Conclusion Maternal cigarette smoking decreases the risk of PIH and eclampsia, with a significant inverse exposure–response relationship apparent for eclampsia. [ABSTRACT FROM AUTHOR]