345: Timing of delivery in women with preexisting hypertension

Abstract

In women with preexisting hypertension (PHTN), it is not clear if routine induction of labor (IOL) before 40 weeks of gestation confers benefit to mother and newborn. Our objective was to compare pregnancy outcomes between women with PHTN who had IOL at either 38 or 39 weeks and those who were managed expectantly during the corresponding weeks using a large population-based cohort. The study group included all women with PHTN who had a singleton birth at ≥ 38 weeks gestation in Ontario, Canada from April 2012-March 2016. Data were obtained from the Better Outcomes Registry & Network (BORN) Ontario, BORN Information System (BIS) database. Women who underwent IOL at 38+0 to 38+6 weeks for PHTN (38-IOL group, N=225) were compared to those who remained undelivered at 39+0 weeks (38-Exp group, N=1,365). Separately, women who underwent IOL at 39+0 to 39+6 weeks for PHTN (39-IOL group, N=213) were compared to women who remained undelivered at 40+0 weeks (39-Exp group, N=669). Out of 462,334 women who delivered during the study period, 3,213 (0.7%) had PHTN, and of these, 2,075 (64.6%) met the study inclusion criteria. Women in the 39-IOL group were less likely to have Cesarean delivery (17.8% vs. 26.3%, p=0.01, aOR 0.59, 95%-CI 0.38-0.93) but had a higher rate of neonatal jaundice requiring phototherapy (5.6% vs. 2.1%, p=0.02, aOR 2.68, 95%-CI 1.13-6.37) compared with women in the 39-Exp group (Table). These differences were not observed in the case of IOL at 38 weeks. There were no other differences in neonatal outcomes between the IOL and expectant management groups at either 38 or 39 weeks (Table). The rate of superimposed preeclampsia in women who were managed expectantly at 38 and 39 weeks was 23.1% and 23.2%, respectively. In women with PHTN, routine IOL at 39 weeks is associated with a lower risk of CS and can prevent subsequent superimposed preeclampsia, but is associated with a small increase in the risk of neonatal jaundice requiring phototherapy.