Effect of uncomplicated chronic hypertension on the risk of small-for-gestational age birth.

This study assesses the effect of chronic hypertension on fetal growth. A cohort of 1,938 pregnant women attending five prenatal clinics in France between August 1991 and May 1993 were enrolled in a prospective study. Chronic hypertension was defined according to blood pressure at enrollment and past history, and cases complicated by preeclampsia were excluded. Adjusted odds ratios of small-for-gestational age birth were estimated by logistic regression. The independent effect of chronic hypertension on mean birth weight was examined through multiple linear regression analysis adjusting for gestational age at delivery and potential confounders. Uncomplicated chronic hypertension was associated with an increased risk of small-for-gestational age birth. Odds ratios increased with age. In women over age 30 years, the association was strong (adjusted odds ratio = 8.5, 95% confidence interval 2.9-24.5). Multiple linear regression showed that mean birth weight was 161 g (95% confidence interval 66-256 g) less in women with chronic hypertension compared with normotensive women. The authors conclude that mean birth weight is reduced and the risk of small-for-gestational age birth is increased in uncomplicated chronic hypertension compared with normotensive pregnancies. Results further suggest that the magnitude of this association increases with age.