Effect of Hypertensive Diseases in Pregnancy on Birthweight, Gestational Duration, and Small-or-Gestational-Age Births

We measured the impact of hypertensive disorders in pregnancy (chronic hypertension, pregnancy-induced hypertension, and eclampsia) on birthweight, gestational duration, and small-for-gestational-age births. We employed a retrospective cohort design using North Carolina birth certificate data for the years 1988-1990, with the analyses based on nearly 300,000 pregnancies. Women noted to have eclampsia during pregnancy had a substantially greater risk of delivering very-low-birthweight infants (birthweight < or = 1,499 gm; risk difference (RD) = 6.7%) and moderately-low-birthweight infants (1,500-2,499 gm; RD = 14.6%), and very preterm (gestational age < 33 weeks; RD = 7.1%) and moderately preterm (33-36 weeks; RD = 9.3%) births, compared with women without hypertension. Corresponding risk differences for these outcomes were 1.9% and 5.1% for very low and moderately low birthweight, and 1.6% and 3.0% for very preterm and moderately preterm for women with chronic hypertension. Risk differences were of similar magnitude for women with pregnancy-induced hypertension for these outcomes. Hypertensive disorders in pregnancy were associated with small-for-gestational-age infants, with risk differences of 5.1%, 3.5%, and 9.2% for chronic hypertension, pregnancy-induced hypertension, and eclampsia, respectively. The patterns of risk were similar for preterm births due to spontaneous onset of labor and those due to other precipitating events. We observed similar patterns for black and white women. Control for confounders through multivariable logistic regression models did not alter the observed patterns. In spite of the limited data quality, we found that hypertensive disorders in pregnancy substantially increase the risk of low birthweight, preterm births, and small-for-gestational-age births.