Stillbirth causes, risk factors revealed by collaborative studies
Woodruff Health Sciences Center | Dec. 13, 2011
In the United States, one out of every 160 pregnancies ends in stillbirth. Two studies published in the December 14 issue of JAMA found that common causes for stillbirth include obstetric complications and placental abnormalities, while factors that could be known at the start of pregnancy, such as previous stillbirth or pregnancy loss, also are associated with an increased risk for stillbirth.
Emory is one of five clinical sites in the Stillbirth Collaborative Research Network, funded by the National Institute of Child Health and Human Development of the National Institutes of Health. Carol Hogue, PhD, MPH, and Barbara J. Stoll, MD, co-lead the Emory site for the network and served as co-authors for the studies.
Hogue is the Terry Professor of Maternal and Child Health, professor of epidemiology and director of the Women’s and Children’s Center at the Rollins School of Public Health. Stoll is the George W. Brumley, Jr. Professor and chair of the Department of Pediatrics at Emory University School of Medicine, chief academic officer of Children's Healthcare of Atlanta, and president of the Emory-Children's Center.
“Stillbirth is still very much an under-recognized issue in the United States,” Hogue says. “These studies are an important step in identifying women who are at greater risk of this type of devastating loss.”
According to Hogue, this is the first study to determine the causes of stillbirth in a racially and geographically diverse population in the United States. Researchers found that obstetric complications and placental abnormalities were the most common causes of stillbirth, while genetic abnormalities, infection, umbilical cord abnormalities, hypertensive disorders and maternal medical complications also contributed.
“To reduce the number of stillbirths, we have to learn what is causing them in the first place,” Stoll says. “This study underscores the importance of performing a full evaluation after the stillbirth, including an autopsy and placental evaluation, so that we can use available tools to determine the cause of death and aim to prevent it in the future.”
Because of the racial distribution in Atlanta, the Emory site added to the diversity of patients who were included in the national study. Researchers found that non-Hispanic black women experienced more stillbirths associated with obstetric complications compared with non-Hispanic white women and Hispanic women combined. Cord abnormalities were associated with more stillbirths in non-Hispanic white and Hispanic women compared with non-Hispanic black and other women.
Another study in the December 14 JAMA, conducted by the Stillbirth Collaborative Research Network Writing Group, examined the relationship between risk factors that could be addressed in the early stages of pregnancy, particularly the contribution of these factors to racial disparities in stillbirth.
“We found that several maternal factors are associated with stillbirth, including ethnicity, diabetes, maternal age over 40 and AB blood type, “ Hogue says. “Those factors we cannot change. There are risk factors associated with stillbirth, however, that we can work on modifying such as drug use, cigarette smoking and being overweight or obese.”
Women who had previous stillbirths or who had never given birth also had an increased risk of stillbirth.
“Overall, pregnancy factors known at the start of pregnancy account for little of the stillbirth risk,” Stoll says. “Apart from occurrence of previous stillbirth or pregnancy loss, the other risk factors have limited predictive value, but they are still important. Having greater knowledge of these risk factors allows us to look for interventions and preventative approaches that aim to reduce the prevalence of stillbirth.”