469: Epidemiology of antepartum versus intrapartum stillbirth in the United States: Heterogeneous etiologies

Abstract

Stillbirth (SB) can occur in the antepartum (AP) or intrapartum (IP) period. We examined the epidemiologic risk profiles of AP and IP SB in the US. We performed a cross-sectional analysis of singleton births (20-44 weeks) in the US between 2015-17 utilizing vital statistics data. Rates of SB were examined overall and in relation to occurrence AP vs. IP. Rates were also examined in relation to maternal race/ethnicity, age, parity, education, marital status, pre-pregnancy BMI, assisted reproduction methods, and medical and obstetric complications. We fit log-linear regression models to estimate the rate ratio (95% confidence interval [CI]) of SB in relation to risk factors. Among 11,463,054 births, the overall SB rate was 5.6 per 1000 (n=64,604). Rates of AP, IP, and missing designation of SB were 2.4 (n=27,732), 0.4 (n=5,114), and 2.7 (n=31,758) per 1000 births, respectively. The rate of AP SB increased with parity from 1.5 for para 1 to 4.8 per 1000 for parity ≥3. IP SB rates tripled from para 1 (0.3 per 1000) to parity ≥3 (0.9 per 1000). Non-Hispanic black women had the highest rate of AP and IP SB 4.4 and 0.9 per 1000, respectively, compared to non-Hispanic white (2.1 and 0.4 per 1000 for AP and IP, respectively), and Hispanic women (1.8 and 0.3 per 1000 for AP and IP, respectively). Women with education levels beyond college had a SB risk of 1.4 per 1000 AP and 0.2 per 1000 IP compared to women with education level below high school who had a risk of 2.6 and 0.6 per 1000, respectively. Both AP and IP SB rates demonstrate a U-shaped curve with increased risk of SB at the extremes of age. Pre-gestational diabetes and chronic hypertension were associated with a 3-fold increase in IP SB risk with rates of 1.5 per 1000 and 1.3 per 1000 respectively. AP SB risk is higher than IP risk. Pre-gestational diabetes and chronic hypertension more than tripled that risk. Non-Hispanic black race was associated with the highest SB rate both AP and IP as were low levels of education, potentially highlighting the impact of racial and socioeconomic disparity.