Chronic hypertension, pregnancy-induced hypertension, and low birthweight.

We examined the associations between chronic hypertension, pregnancy-induced hypertension, and low birthweight in a retrospective cohort study using Washington birth certificate data. The adjusted prevalence ratio for low birthweight associated with chronic hypertension was 3.9 [95% confidence interval (CI) = 3.4-4.4]. The prevalence ratio for pregnancy-induced hypertension associated with chronic hypertension ranged from 3.6 (95% CI = 3.2-4.1) for primiparous women to 10.7 (95% CI = 8.7-13.2) for multiparous women. The association of chronic hypertension and low birthweight could not be explained by the increased risk of pregnancy-induced hypertension in these women.