366: Risk factors associated with early stillbirth in women with chronic hypertension

Abstract

Risk of stillbirth in women with chronic hypertension (CHTN) is 6-25 per 1,000, approximately 2-fold higher than women without CHTN. ACOG recommends initiation of antepartum fetal surveillance (ANFS) no earlier than 32 weeks’ gestation for most women with CHTN. We sought to quantify the cumulative proportion of stillbirths in women with CHTN by gestational age (GA) and to identify risk factors associated with earlier stillbirth (<32 wks) in this population. Population-based retrospective cohort study of all stillbirths in the U.S. during the year of 2014. Frequency of stillbirth in women who were antenatally diagnosed (non-laboring) with fetal demise were stratified by GA, from 20 to 44 weeks, according to CHTN status. Cause of fetal death was obtained from ICD-10 codes. Maternal and obstetric characteristics were compared between those with and without CHTN and then subsequently for those with early (<32 weeks) stillbirth vs late (≥32 weeks) stillbirth among women with CHTN. Multivariate logistic regression estimated the relative association between CHTN and various maternal, obstetric, and fetal factors. There were 14,954 non-laboring women diagnosed with antepartum (non-laboring) stillbirth during 2014 in the US in which CHTN status was recorded. Of those, 14,954 stillbirths, 793 (5.3%) women had CHTN. Median GA of antepartum stillbirth diagnosis was 27 (IQR 23,34) weeks vs 29 (IQR (23,36) weeks (p<0.001) between women with and without CHTN, respectively. The cumulative rates of stillbirth by GA among women with CHTN where cause of fetal death was attributed to “maternal hypertensive disorder” were 34.1, 59.9, 75.4, 82.3, and 90.1% at 24, 28, 32, 34, and 36 weeks’ gestation, respectively. Women with CHTN had higher rates of obesity, diabetes, and stillbirth < 32 wks (67.0 vs 58.7%, p<0.001; aRR 1.9, CI 1.5-2.5) compared to women without CHTN. Factors associated with early stillbirth among women with CHTN included lagging fetal growth as evidenced by small for gestational age (SGA <10th%) birthweight (aRR 1.6, CI 1.1-2.3), Black race (aRR 1.8, CI 1.3-2.6), and primiparity (aRR 1.4, CI 1.0-2.1). Stillbirth occurs at an earlier GA among women with CHTN compared to those without. More than 50% of stillbirths attributed to maternal hypertensive disorders occurred before 27 wks and over 70% occurred before 32 wks. Current ANFS guidelines may fail to prevent the majority of antepartum stillbirths among women with CHTN.View Large Image Figure ViewerDownload Hi-res image Download (PPT)