Risk factors for late (28+ weeks’ gestation) stillbirth in the United States, 2014–2015

PLOS ONE RESEARCH ARTICLE Risk factors for late (28+ weeks’ gestation) stillbirth in the United States, 2014–2015 Darren Tanner1*, Sushama Murthy1¤, Juan M. Lavista Ferres1, Jan-Marino Ramirez2,3, Edwin A. Mitchell ID4 1 AI for Good Research Lab, Microsoft Corporation, Redmond, WA, United States of America, 2 Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, WA, United States of America, 3 Departments of Neurological Surgery and Pediatrics, School of Medicine, University of Washington, Seattle, WA, United States of America, 4 Department of Paediatrics, Child and Youth Health, The University of Auckland, Auckland, New Zealand a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 ¤ Current address: Meta Reality Labs, Meta, Menlo Park, CA, United States of America * Abstract OPEN ACCESS Citation: Tanner D, Murthy S, Lavista Ferres JM, Ramirez J-M, Mitchell EA (2023) Risk factors for late (28+ weeks’ gestation) stillbirth in the United States, 2014–2015. PLoS ONE 18(8): e0289405. https://doi.org/10.1371/journal.pone.0289405 Editor: Samantha Frances Ehrlich, University of Tennessee Knoxville, UNITED STATES Background In the United States (US) late stillbirth (at 28 weeks or more of gestation) occurs in 3/1000 births. Aim We examined risk factors for late stillbirth with the specific goal of identifying modifiable factors that contribute substantially to stillbirth burden. Received: October 8, 2022 Accepted: July 5, 2023 Published: August 30, 2023 Copyright: © 2023 Tanner et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All data underlying the results presented in the study are available from the United States Centers for Disease Control Vital Statistics Online Data Portal (https://www.cdc. gov/nchs/data_access/vitalstatsonline.htm). Funding: DT, SM, and JLF received salary from Microsoft Corporation while conducting this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section. Setting All singleton births in the US for 2014–2015. Methods We used a retrospective population-based design to assess the effects of multiple factors on the risk of late stillbirth in the US. Data were drawn from the US Centers for Disease Control and Prevention live birth and fetal death data files. Results There were 6,732,157 live and 18,334 stillbirths available for analysis (late stillbirth rate = 2.72/1000 births). The importance of sociodemographic determinants was shown by higher risks for Black and Native Hawaiian and Other Pacific Islander mothers compared with White mothers, mothers with low educational attainment, and older mothers. Among modifiable risk factors, delayed/absent prenatal care, diabetes, hypertension, and maternal smoking were associated with increased risk, though they accounted for only 3–6% of stillbirths each. Two factors accounted for the largest proportion of late stillbirths: high maternal body mass index (BMI; 15%) and infants who were small for gestational age (38%). Participation PLOS ONE | https://doi.org/10.1371/journal.pone.0289405 August 30, 2023 1 / 20 PLOS ONE Competing interests: DT, SM, and JLF received salary from Microsoft Corporation while conducting this study. There are no patents, products in development or marketed products associated with this research to declare. This does not alter our adherence to PLOS ONE policies on sharing data and materials. Risk factors for late stillbirth in the United States, 2014–2015 in the supplemental nutrition for women, infants and children program was associated with a 28% reduction in overall stillbirth burden. Conclusions This study provides population-based evidence for stillbirth risk in the US. A high proportion of late stillbirths was associated with high maternal BMI and small for gestational age, whereas participation in supplemental nutrition programs was associated with a large reduction in stillbirth burden. Addressing obesity and fetal growth restriction, as well as broadening participation in nutritional supplementation programs could reduce late stillbirths. Introduction Fetal loss is the death of the fetus during pregnancy or labor. In the United States (US) a death that occurs prior to 20 weeks’ gestation is usually classified as either a spontaneous miscarriage or termination of pregnancy; those occurring after 20 weeks constitute a stillbirth. Because of differences in reporting and definitions of stillbirth across countries, the World Health Organization (WHO) uses fetal deaths from 28 weeks’ gestation for international comparisons. Using this definition more than 2.6 million stillbirths occur per year worldwide, most of which are in low and middle-income countries where they are frequently related to lack of access to adequate care in pregnancy and labor [1]. In high-income countries, stillbirth rates declined markedly between 1940 and 1990 due largely to improvements in maternity care [2]. However, this decline has slowed: between 1990 and 2008, late stillbirth rates declined by only 14% across 12 high-income countries [3]. Since then, the decline in late stillbirth rates in the US has further slowed: rates plateaued between 2006 (2.97/1000 births) and 2012 (2.96/1000) [4], though the rate had declined slightly by 2019 (2.73/1000), although at least part of this reported decrease is due a change in definition used to measure gestational age [5]. Rates also vary between high-income countries. In the US in 2015 the late stillbirth rate was 3.0/1000 births compared with Iceland 1.3/1000, Denmark 1.7/1000, The Netherlands 1.8/ 1000, Norway 2.2/1000 and UK 2.9/1000 [6]. This suggests there is considerable room for improvement in the US. Known risk factors for stillbirth in high-income countries include mothers who are nulliparous, have a plural pregnancy, are older, belong to ethnic minority groups, experience socioeconomic disadvantage, have high BMI, smoke tobacco, have delayed or absent prenatal care, have diabetes, and/or have hypertension [7]. However, most of the studies reporting these factors have defined stillbirth as occurring after 20 weeks’ gestation rather than the WHO’s 28 weeks’ definition. The Stillbirth Collaborative Research Network has shown that the cause of stillbirth varies by gestational age, with relative rates of causes differing between those that occur between 20–27 weeks of gestation (“early” stillbirth) and those occurring at 28 completed weeks of gestation or more (“late” stillbirth): obstetric complications were the cause in 39.8% of early but only 17.4% in late stillbirths; infections were implicated in 16.9% of early but (...truncated)