Similar associations of parental prenatal smoking suggest child blood pressure is not influenced by intrauterine effects

Maternal smoking in pregnancy may be associated with higher offspring blood pressure; however, results of previous studies have been inconsistent and included varying confounder adjustments. We studied the association between maternal smoking in pregnancy and offspring blood pressure at 7 years in the Avon Longitudinal Study of Parents and Children, accounting for important social and environmental confounders and using partner smoking to investigate intrauterine effects. Analysis was carried out in 6509 children with maternal smoking data and 7149 children with partner smoking data. In models adjusting for child age and sex, modest differences in systolic blood pressure were observed between children of mothers who did and did not smoke during pregnancy ( beta = 0.64 mm Hg; 95% CI: 0.09 to 1.20; P = 0.02). Adjusting for all of the confounders attenuated this difference toward the null ( beta = 0.05 mm Hg; 95% CI: -0.59 to 0.68; P = 0.9), mostly because of adjustment for breastfeeding, maternal education, and family social class. Associations were similar between maternal and partner smoking with offspring systolic blood pressure ( for partner smoking: beta = 0.62 mm Hg; 95% CI: 0.17 to 1.07; P = 0.07 minimally adjusted and beta = 0.26 mm Hg; 95% CI: -0.36 to 0.87; P = 0.4 fully adjusted), providing further evidence that differences in child blood pressure observed in minimally adjusted models are not because of a biological influence of maternal smoking on the intrauterine environment.