Gestational weight gain and adverse pregnancy outcomes by pre-pregnancy BMI category in women with chronic hypertension: A cohort study.

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It is important to understand relationships of gestational weight gain with adverse pregnancy outcomes in women with chronic hypertension, given their high baseline risk of adverse outcomes. We assessed associations of gestational weight gain with adverse pregnancy outcomes in women with chronic hypertension by pre-pregnancy body mass index categories. We identified 14,369 women with chronic hypertension using electronic health records from 3 integrated health care delivery systems (2005-2014). Gestational weight gain-for-gestational age charts were used to calculate gestational weight gain z-scores, which account for gestational age. Modified Poisson regression models using generalized estimating equations were used to calculate relative risks and 95% confidence intervals, adjusted for sociodemographic and medical characteristics. Preeclampsia, preterm delivery, cesarean delivery, neonatal intensive care unit admission, birthweight (extracted from the electronic health record). In women with normal weight or overweight, low gestational weight gain (z-score<-1) was associated with 27-28% greater risk of preterm delivery and 48-82% greater risk of small-for-gestational age birthweight, while high gestational weight gain (z-score>1) was associated with 40-90% greater risk of preeclampsia and 59-113% greater risk of large-for-gestational age birthweight. In women with obesity, low gestational weight gain was associated with 27-54% lower risk of several adverse pregnancy outcomes, including preeclampsia and cesarean delivery. In women with chronic hypertension and normal weight or overweight, moderate gestational weight gain may confer the lowest risk of adverse outcomes. In women with chronic hypertension and obesity, low gestational weight gain may be necessary for the lowest risk of adverse pregnancy outcomes.