December 14, 2011
Researchers Identify Causes And Risk Factors For Stillbirth
According to a recent study, published today in the Journal of the American Medical Association (JAMA), the most common causes of stillbirth differ depending on a number of factors, including race, ethnicity, previous pregnancy outcomes, and range of health -- and typically all identifiable before or at the start of pregnancy.
“Stillbirth, defined as fetal death at 20 weeks´ gestation or later, is one of the most common adverse pregnancy outcomes in the United States and affects approximately 1 in 160 pregnancies. These approximately 26,000 stillbirths per year are equivalent to the number of infant deaths. The stillbirth rate in the United States is higher than that of many other developed countries,” states background information in the study. “Since 2003 the stillbirth rate in the United States has remained stagnant at 6.2 stillbirths per 1,000 births, 59 percent higher than the Healthy People 2010 target goal of 4.1 fetal deaths per 1,000 births.”
The study took place over 30 months -- from March 2006 to September 2008 -- at nearly 60 US 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.
The research team, led by Robert M. Silver M.D., of the University of Utah School of Medicine in Salt Lake City, 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 has shown that black women are more than twice as likely to be affected by stillbirth as white women, but the reasons behind this are not known. The researchers in the new study 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.
The authors note that the sources most likely to provide positive information regarding cause of death were placental histology, prenatal postmortem examination, and karyotype (an evaluation of the chromosomes).
“Stillbirth is more common than people realize, affecting one out of every 160 pregnancies in the United States,” said Silver. “Our research focuses on determining underlying causes of stillbirth, as well as factors that may contribute to the significant racial disparity in stillbirth rates.”
“Reduction in the stillbirth rate will require thorough investigation into the cause of death. After a systematic and thorough evaluation, a cause of death was determined in the majority of cases of stillbirth in our study. Therefore, postmortem examination, placental histology, and karyotype are strongly recommended as part of the diagnostic evaluation. In addition, the development of interventions to prevent stillbirth should consider the observed differential distribution of causes of death as gestational age advances, as well as variation by race/ethnicity,” the research team concludes.
The data in this study coincides with findings from a joint study, also published in Wednesday´s issue of JAMA. In the second study, George R. Saade, M.D., of the University of Texas Medical Branch at Galveston, and colleagues with the Stillbirth Collaborative Research Network Writing Group, examined the relation between stillbirths and risk factors that could be ascertained at the start of pregnancy, particularly the contribution of these factors to the racial disparities that exist with stillbirths.
“Many of the factors associated with stillbirth need to be addressed early in pregnancy. Although other factors may be important later in pregnancy, clinicians providing obstetrical care frequently spend relatively more time at the initial visits counseling patients regarding their risk of adverse pregnancy outcomes,” write authors of the study.
“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 Saade, adding 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.”
“It is extremely difficult to predict stillbirth risk based on risk factors that can be identified at the start of a pregnancy. The more we learn about causes and risk factors for stillbirth, the better we will become at designing strategies to reduce or prevent stillbirth,” said Silver.
“Further research is needed to identify pregnancies at highest risk overall and for specific causes,“ note the researchers.
The SCRN was established by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) 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.
On the Net:
- Study Abstract
- Stillbirth Collaborative Research Network (SCRN)
- University of Texas Medical Branch (UTMB)
- University of Utah School of Medicine