Parental smoking in pregnancy and the risks of adult-onset hypertension.

Fetal exposure to parental smoking may lead to developmental adaptations and promote various diseases in later life. This study evaluated the associations of parental smoking during pregnancy with the risk of hypertension in the daughter in adulthood, and assessed whether these associations are explained by birth weight or body weight throughout life. We used data on 33086 participants of the Nurses' Health Study II and the Nurses' Mothers' Cohort. Cox proportional hazards models were used to examine the associations of maternal and paternal smoking during pregnancy with the nurse daughter, with self-reported physician-diagnosed hypertension from 1989 until 2007. Overall, 8575 (25.9%) mothers and 18874 (57.0%) fathers smoked during pregnancy. During follow-up, 7825 incident cases of adult-onset hypertension were reported. Both maternal and paternal smoking of ≥ 15 cigarettes/d during pregnancy were associated with increased risks of hypertension (rate ratio, 1.19; 95% CI, 1.09-1.29; and rate ratio, 1.18; 95% CI, 1.12-1.25, respectively) in the age-adjusted models. Further adjustment for birth weight did not affect the effect estimates appreciably, whereas additional adjustment for body shape and weight until age 18, or current body mass index, attenuated the associations with both maternal and paternal smoking (rate ratio, 1.07; 95% CI, 0.98-1.16; and rate ratio, 1.06; 95% CI, 1.01-1.12, respectively). The associations of parental smoking during pregnancy with the risk of hypertension in the offspring were largely explained by body weight throughout life, suggesting that these associations may not reflect direct intrauterine mechanisms.