Abstract
Background: Recent literature suggest the effect of maternal smoking on risk of hypertensive disorders in pregnancy (HDP) and preeclampsia may differ by ethnicity, however studies on Asians are limited.
Methods: We investigated the association between maternal smoking and HDP and preeclampsia, by using a common analysis protocol to analyze the association in six birth cohorts participating in a Japanese consortium of birth cohorts (JBiCC). Results were compared with published results from cohorts not included in this consortium, and where possible produced a meta-analysis including these studies.
Results: Meta-analysis of four cohort studies including 28,219 participants produced an odds ratio (OR) of 1.24 (95% confidence interval (CI) 0.88-1.87) for effect of smoking beyond early pregnancy compared to women who did not smoke during pregnancy. These results combined with those from the Japan Environment and Children’s Study (JECS) yielded an OR of 1.19 (95%CI 1.00-1.43, p=0.056). Meta-analysis results for categories of smoking volume were insignificant, but when combined with JECS yielded an OR of 0.86 (95%CI 0.65-1.12) for smoking 1-4 cigarettes, 1.25 (95%CI 0.98-1.60) for smoking 5-9 cigarettes, and 1.27 (95%CI 1.04-1.54) for smoking 10 or more cigarettes per day. All effects were insignificant for preeclampsia.
Conclusion: Our results suggest the protective effect of smoking longer, smoking more on HDP and preeclampsia repeatedly observed among Europeans and North Americans likely do not hold for the Japanese.
