Levels, Trends, and Risk Factors for Stillbirths in the United States: 2000–2017

Abstract

Objective: This study documents 2000-2017 trends in stillbirth rates and changes in associations between known maternal and fetal risk factors and stillbirths for 2000-2002 versus 2015-2017 in the US. Study design: We conducted a retrospective, population-based analysis of stillbirths and live-births using national vital statistics data. We calculated annual stillbirth rates overall and by gestational age; and examined rates by maternal age, race-ethnicity, and state for 2000-2002 versus 2015-2017. We used chi-squared tests to examine associations between maternal and fetal risk factors for early (20-27 weeks) and late (28+ weeks) stillbirths compared to live-births for 2000-2002 versus 2015-2017. Results: Stillbirth rates declined 7.5% (p<0.001) during 2000-2006 but remained flat at about 6 stillbirths per 1,000 births thereafter. Throughout 2000-2017, there were significant improvements in stillbirth rates at 39+ weeks nationally (p<0.001), but rates varied greatly between and within states. Socio-demographic factors (advanced maternal age, Black race, low education, unmarried status, rural residence), obstetric and other medical factors (3+ births, infertility treatment, obesity, diabetes, chronic hypertension, eclampsia, no prenatal care, tobacco use) were significantly more prevalent in women with late than early stillbirths or live-births. Notably, late and total stillbirth rates were about 30% higher for women 35+ than for women <35 years and twice as high for non-Hispanic Black than non-Hispanic White women; American Indian/Alaska Native women represented the only racial-ethnic group with significantly higher late stillbirth rates in 2015-2017 than in 2000-2002. Pregnancy and fetal factors (multiple pregnancy, male fetus, breech presentation) were more prevalent in women with early than late stillbirths or live-births. Conclusion: US stillbirth rates have plateaued since 2006. There are persistent differential risk profiles for early versus late stillbirths, which can inform stillbirth prevention strategies (e.g., close observation of women with risk factors for stillbirth) and new research into causes of stillbirths by gestational age.