Researchers at Mass General Brigham and Harvard TH Chan School of Public Health have identified greater rates of stillbirth in the United States than previously reported, publishing their findings in JAMA.1
Many of the identified stillbirths, especially those at 40-weeks’ gestation or later, did not have any identified clinical risk factors. According to investigators, this highlights a need for additional research about factors influencing socioeconomic differences in stillbirth rates. These include social, health system, and clinical risk factors.
Key takeaways:
- A new analysis of 2.7 million US pregnancies found a stillbirth rate of 1 in 150 births—higher than the CDC’s previously reported rate of 1 in 175.
- Nearly 28% of stillbirths occurred without any identifiable clinical risk factors.
- The highest proportion of unexplained stillbirths occurred at 40-weeks’ gestation or later.
- Rates were significantly higher among patients in low-income areas and regions with more Black patients than White patients.
- Researchers emphasized the urgent need for better tools to predict and prevent stillbirths, particularly in late-term pregnancies.
“Stillbirths impact nearly 21,000 families each year in the US, and nearly half of those occurring at 37+ weeks are thought to be preventable. Yet there is very little research in this area,” said Jessica Cohen, PhD, co-senior author and professor of health economics at Harvard. “Our study highlights the pressing need to improve stillbirth risk prediction and prevention.”
Clinical and obstetric risk factors
There were over 2.7 million US pregnancies from 2016 to 2022 included in the analysis. Data was obtained from health insurance claims, the Health Care Cost Institute, the American Community Survey, and the March of Dimes. Among this population, 18,893 stillbirths were identified.
Clinical factors assessed for links to stillbirth included pregnancy-related and chronic hypertension, obesity, pre-pregnancy and gestational diabetes, and substance use. Fetal risk, such as growth restriction, decreased movement, and anomalies, were also included. Finally, obstetric risks included prior stillbirth, low or excess amniotic fluid levels, and adverse pregnancy outcomes.
Stillbirth was reported in 1 in 150 births. In comparison, the previous reported CDC rate was 1 in 175 births, highlighting a greater prevalence than expected. Further increases were reported for patients residing in low-income areas and in regions with more Black patients than White patients, at 1 in 112 births and 1 in 95 births, respectively.
Differences in stillbirth rates were not reported based on rurality and levels of access to obstetric care. However, nearly 27.7 of stillbirths did not have an identified clinical risk factor.
Late-gestation stillbirths
The most significant rates of stillbirth among patients with no clinical risk factor were reported in later gestational ages. Of stillbirths, no risk factors were identified in:
- 24.1% at 38-weeks’ gestation
- 34.2% at 39-weeks’ gestation
- 40.7% at 40-weeks’ gestation or later.
Pregnancies with low amniotic fluid levels, fetal anomalies, and chronic hypertension had the greatest stillbirth rates. Investigators concluded interventions are needed to improve stillbirth prediction, especially later in pregnancy.
“Although momentum toward improving stillbirth research and prevention efforts has increased in recent years, rates in the US remain much higher than in peer countries,” said Mark Clapp, MD, MPH, co-senior author and maternal-fetal medicine provider at Massachusetts General Hospital.
Managing prolonged pregnancies
Methods of managing pregnancies reaching increased gestational ages have been highlighted by Ulla-Britt Wennerholm, MD, a medical doctor and professor of obstetrics at Sahlgrenska University Hospital, in an interview with Contemporary OB/GYN.2 Active labor and induction were noted as 2 potential methods with a need to balance the risks and benefits.
According to Wennerholm, decisions should be individualized based on each patients’ circumstances. Clear communication can allow patients to understand risks such as stillbirth, alongside benefits from active management and labor induction. Future research may allow optimization of managing prolonged pregnancies.
