Study Gives Insight into Most Common Causes, Risks Factors for Stillbirth

Preterm labor, abnormalities of placenta, infection are among contributors

The Stillbirth Collaborative Research Network (SCRN) has reported that performing a systematic medical evaluation leads to a probable or possible cause of death in the majority of stillbirths. According to a study published in the Wednesday, Dec. 14, 2011, issue of the Journal of the American Medical Association (JAMA), the most common causes of stillbirth differ across racial and ethnic groups, with resulting implications for monitoring and prevention of this devastating pregnancy outcome.

The researchers found that the most common causes of stillbirth were obstetric conditions, such as cervical insufficiency, placental abruption, or preterm labor, and abnormalities of the placenta. Other common causes included genetic or structural abnormalities of the fetus, umbilical cord abnormalities, infection, blood pressure disorders, and other maternal medical conditions. Previous research shows that black women are more than twice as likely to be affected by stillbirth as white women, but the reasons for this disparity are as yet unknown. In this study, the researchers discovered that stillbirths in black women were more likely to occur earlier in the pregnancy or during childbirth and were more likely to be caused by obstetrical complications or infection.

“Stillbirth is more common than people realize, affecting one out of every 160 pregnancies in the United States,” says Robert M. Silver, M.D., professor of obstetrics and gynecology, chief of the Division of Maternal-Fetal Medicine at the University of Utah School of Medicine, and senior author on the study. “Our research focuses on determining underlying causes of stillbirth, as well as factors that may contribute to the significant racial disparity in stillbirth rates.”

There are approximately 26,000 stillbirths a year in the United States, equivalent to the number of infant deaths that occur each year. Although the stillbirth rate declined steadily from 1990 to 2003, it has remained stagnant since 2003 and is higher than that of many other developed countries. SCRN was created by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) to address this major public health issue. The main objectives of the SCRN include ascertaining the causes and risk factors for stillbirth and finding reasons for racial disparities.

For this study, the SCRN recruited a racially and geographically diverse population from 59 hospitals in five states, including Utah. SCRN researchers performed complete postmortem examinations on 512 of the 972 stillbirths that occurred in the study areas from March 2006 to September 2008. These postmortem examinations included autopsy, evaluation of the placenta by a perinatal pathologist, and chromosome testing, in addition to laboratory studies and an interview with the mother. By performing systematic evaluations, the researchers were able to identify a probable or possible cause of death in 390, or 76 percent, of the stillbirths.

“Evaluations for causes of stillbirth are often incomplete or absent due to limited availability of services, concerns about cost, or difficulty in discussing death or postmortem examination,” says Silver. “However, performing a thorough investigation to determine a cause may actually help to facilitate closure or alleviate guilt for patients and physicians affected by stillbirth. It can also help in counseling patients about recurrence risk and, in some cases, guide medical interventions to improve outcomes in subsequent pregnancies.

“The consistent and persistent racial disparity in stillbirth remains largely unexplained,” says Silver. “It is well-documented that black women are also more likely to have spontaneous preterm birth, so perhaps there are genetic or other factors that contribute to both stillbirth and spontaneous preterm birth in black women.”

A second study conducted by SCRN, also published in the same issue of JAMA, examined the relationship between stillbirths and risk factors that could be determined at the start of pregnancy. This study revealed that multiple factors, including black ethnicity, previous still birth, never having given birth, prior pregnancy loss, diabetes, maternal age, marital status, and excess weight, were associated with an increased risk of stillbirth. However, these risk factors accounted for only a small proportion of overall stillbirth risk.

“It is extremely difficult to predict stillbirth risk based on risk factors that can be identified at the start of a pregnancy,” says Silver. “The more we learn about causes and risk factors for stillbirth, the better we will become at designing strategies to reduce or prevent stillbirth.”

Michael W. Varner, M.D., professor and vice-chair for research in obstetrics and gynecology at the University of Utah, is a co-author on these two studies. Currently, SCRN is conducting additional research examining genetic, infectious, psychosocial, and even emotional factors, such as stress, that may contribute to stillbirth risk or better explain the persistent racial disparity in the rates of stillbirth.

SCRN was established by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) to study the extent and causes of U.S. stillbirths. The network includes: University of Utah School of Medicine; University of Texas Medical Branch at Galveston; Brown University School of Medicine; University of Texas Health Science Center at San Antonio; Drexel University School of Medicine; Emory University School of Medicine and Rollins School of Public Health; RTI International; NICHD.

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