An obstetrical paradox is that maternal smoking is protective for the development of preeclampsia. However, there are no prior studies investigating the risk of preeclampsia in women who were exposed to tobacco smoking during their own fetal period. We aimed to study the subsequent risk of preeclampsia in women who were exposed to tobacco smoke in utero, using a national population-based register.
Data were obtained from the Medical Birth Register of Sweden for women who were born in 1982 (smoking data first recorded) or after, who had given birth to at least one child; 153 885 pregnancies were included.
The associations between intrauterine smoking exposure (three categories: non-smokers, 1-9 cigarettes/day [moderate exposure], and >9 cigarettes/day [heavy exposure]) and subsequent preeclampsia (n = 5721) were assessed using logistic regressions. In models adjusted for maternal age, parity and own smoking, the odds ratios (OR) for preeclampsia were 1.06 [95% CI: 0.99,1.13 for moderate intrauterine exposure, and 1.18, [95% CI: 1.10,1.27] for heavy exposure. Estimates were slightly strengthened in non-smoking women who experienced heavy intrauterine exposure (adjusted OR 1.24 [95% CI: 1.14,1.34]). Results were no longer statistically significant after adjustment for the woman's own BMI, gestational age and birthweight Z-scores.
These data revealed some evidence of a possible weak positive association between intrauterine smoking exposure and the risk of subsequent preeclampsia, however, results were not significant over all manifestations of preeclampsia and confounder adjustment. The increased risk might be mediated through exposed women's own BMI or birthweight.