297: Chronic hypertension: Is there an optimal delivery time?

Abstract

To determine the gestational age at delivery for chronic hypertension that is associated with the minimum adverse and maximum beneficial outcomes. This is a retrospective review of 915 (2.2%) patients with a diagnosis of chronic hypertension (CHTN) from 40,683 women who delivered at a single hospital system from 1/2013-12/2016. Gestational age at delivery was categorized as completed weeks from <37 weeks to 41 weeks. The sixteen outcomes studied were: composite adverse neonatal outcomes, neonatal hypoxia, neonatal hypoglycemia, neonatal intensive care unit admission (NICU), FHR abnormalities (including late decelerations, variable decelerations, minimal variability, bradycardia, tachycardia and abnormal FHR ICD-9 code), Apgar at 5 minutes, umbilical artery pH, umbilical artery base excess, neonatal length of stay and maternal readmission. ANOVA, and Jonckheere-Terpstra test were used for test of trends, Chi square test and logistic regression analysis were performed. NICU admission rate decreased steadily from 85.4% at <37 weeks to 17% at 41 weeks. The rate of neonatal hypoxia was lowest at 39-40 weeks and highest at <37 weeks, while for hypoglycemia the rate was lowest at 39-40 weeks and highest at <37 weeks. Most of the fetal heart categories and blood gases levels were most optimum at 39 weeks and least reassuring at <37 weeks and 41weeks. The tests of trend was significant for all outcomes except umbilical artery pH, 5 minute apgar <7 and composite neonatal adverse outcome. Amongst outcomes studied, optimal outcomes occurred in 8(50%) at 39 weeks, 5 (31%) at 40 weeks, 2(13%) at 37 weeks and 41 weeks each, 1(6%) at <37weeks, and 38 weeks each. For suboptimal outcomes, 7(44%) occurred at 41 weeks, 6(38%) occurred at <37 weeks, 2(13%) at 37 weeks, 1(6%) at 40 weeks with none at 38 and 39 weeks. The data suggest that 39 weeks gestation is “safe” and an optimal time to deliver patients with chronic hypertension.