Largest, most comprehensive study finds previous stillbirth, prior pregnancy history strongest indicators of stillbirth risk; lifestyle choices also play a role
Stillbirth is associated with a range of health and socio-demographic factors identifiable before or at the start of pregnancy, including prior pregnancy outcomes, ethnicity and modifiable health factors, such as diabetes, obesity and smoking. These findings are the result of the largest population-based stillbirth study and are reported in the December 14 issue of the Journal of the American Medical Association.
The multi-site study is among the initial publications by the NIH-funded Stillbirth Collaborative Research Network, of which the University of Texas Medical Branch is a member. In the United States, stillbirths account for almost half of the deaths from 20 weeks’ gestation to one year of life and occur in approximately one out of every 160 pregnancies. This study examined risk factors that could be ascertained at the start of pregnancy – at a time when clinicians counsel patients about the risk of adverse pregnancy outcomes.
The research took place over two and a half years at nearly 60 U.S. urban and rural community and academic hospitals with access to at least 90 percent of deliveries within their geographic regions. The study included 614 stillbirths and 1,816 live births. Data collection and evaluation were designed in a manner that would ensure this study was more representative and rigorous than prior studies of stillbirths.
Several reproductive factors were most strongly associated with stillbirth, including previous stillbirth, nulliparity (i.e., never having borne a child) with and without history of miscarriages at fewer than 20 weeks’ gestation, and multiple births in the current pregnancy.
Other factors found to be associated with stillbirth included:
· Non-Hispanic black race/ethnicity;
· Pregnancy after age 40;
· Maternal AB blood type;
· Not living with a partner;
· Smoking during three months prior to pregnancy; and
· History of illicit drug use.
“Moms-to-be and clinicians have a window of opportunity to save babies’ lives by maintaining a healthy weight, managing conditions such as diabetes and stopping all unhealthy behaviors, such as smoking, prior to pregnancy. In fact, obesity may be among the greatest risk factors that we have control over,” said corresponding author Dr. George Saade, Chief of Maternal-Fetal Medicine at UTMB. He added that women with any of these known risk factors should start prenatal care early and that doctors should monitor them closely.
“We were surprised to learn that while these risk factors were significant on their own, they didn’t account for the largest risk of stillbirth. Even if effective, reducing modifiable risks across the board would be unlikely to prevent all stillbirths,” he said. “Other factors – perhaps occurring later in pregnancy – may have more predictive value, either independently or combined with these early risk factors.”
The SCRN was established by the Eunice Kennedy Shriver National Institute of Child Health and Human Development in 2003 to investigate the extent and causes of stillbirth in the United States. The researchers have a study underway looking at potential risk factors that may occur later in pregnancy. Other future studies will explore possible genetic risk factors and how various risk factors may be linked.
Ultimately, the SCRN’s body of research will be used to develop a model to calculate patients’ individual risks so that doctors can take appropriate steps to prevent stillbirth. These include providing those at highest risk with additional monitoring and care and improving our ability to determine the risks and benefits of delivering early versus continuing the pregnancy.
This research was supported by grant funding from the NICHD. In addition to the UTMB team, collaborating institutions and coauthors of this study include the University of Texas Health Science Center at San Antonio; the University of Utah School of Medicine; Emory University School of Medicine and the Rollins School of Public Health; Brown University; RTI International; Pregnancy and Perinatalogy Branch, Eunice Kennedy Shriver NICHD, National Institutes of Health; and Drexel University School of Medicine.