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-forgestational 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-forgestational age birth is increased in uncomplicated chronic hypertension compared with nomnotensive pregnancies. Results further suggest that the magnitude of this association increases with age. Am J Epidemiol 1997; 145:689-95. birth weight; cohort studies; gestational age; hypertension; multivariate analysis; pregnancy; risk factors Chronic hypertension accompanies 0.5-5 percent of all pregnancies (1-3), a frequency in the same range as that of preeclampsia (4, 5). Hypertensive disorders during pregnancy are known to be related to poor fetal outcome (1, 6). The adverse effect of preeclampsia on the fetus is well established. Studies consistently show a link between preeclampsia and impaired fetal growth (7-9), with both disorders probably being the consequence of a common placental disorder (10, 11). Several old, but few recent, studies have addressed the effect of chronic hypertension on fetal outcome. All of these studies showed that among pregnancies complicated by chronic hypertension, the worst perinatal outcome is found in superimposed preeclampsia (1,6,8,12). Studies were contradictory regarding the issue of pregnancies without superimposed preeclampsia (1). On one hand, some authors stated that the excess of morbidity and mortality in pregnancies complicated Received for publication July 23, 1996, and In final form January 16, 1997.Abbreviations: Cl, confidence interval; OR, odds ratio. by chronic hypertension is entirely due to superimposed preeclampsia (3). According to them, the risk of perinatal mortality and fetal growth restriction in pregnancies accompanied by uncomplicated chronic hypertension is similar to the risk in normotensive pregnancies (3,13,14). On the other hand, some studies found an increased risk of perinatal mortality and fetal growth restriction in pregnancies accompanied by uncomplicated chronic hypertension, at least in severe cases ...

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