Studies Identify Stillbirth Risk Factors, Causes

Dec. 13, 2011 -- Although many risk factors for stillbirth are out of a woman's control, others can be changed to help lower risk, new research shows.

The cause of death can be identified for many stillbirths, researchers have also found. That can help parents heal.

"The good news is, a lot of the risk factors that are known early [in pregnancy] are changeable," says researcher George Saade, MD, professor of obstetrics and gynecology and chief of the division of maternal-fetal medicine at the University of Texas Medical Branch at Galveston.

Among those, he and his colleagues found, are losing weight, if needed, and not using illegal drugs. Another risk factor is not smoking during the three months before pregnancy occurs, they found.

Stillbirth, defined as fetal death at 20 weeks into the pregnancy or later, affects one in 160 U.S. pregnancies. In the U.S., about 26,000 infants are stillborn each year. After a decline in stillbirth from 1990 to 2003, the rate has been stagnant.

The new research, funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development, was conducted by the Stillbirth Collaborative Research Network. It was set up to address stillbirth as a public health issue.

The research is published as two studies in the Journal of the American Medical Association.

Stillbirth: Risk Factors Known in Early Pregnancy

Saade and his colleagues evaluated 614 stillborn infants, comparing them to 1,816 infants delivered healthy. The study was done between March 2006 and September 2008 at 59 U.S. hospitals.

After evaluating a number of factors, they found many maternal factors associated with stillbirth. They include:

• Being African-American
• Having diabetes
• Being age 40 or older
• Having AB blood type
• Having a history of illegal drug use with addiction
• Smoking cigarettes in the three months before getting pregnant
• Being overweight or obese
• Not living with a partner
• Having a previous stillbirth
• Carrying multiples

The odds of stillbirth for each risk factor ranged. Smoking during the three months before pregnancy, for instance, raised the odds about 1.5 times; previous stillbirth nearly six-fold.

The research results point to the need for good prenatal care and counseling, Saade tells WebMD. "It's important to start prenatal care early, so that any of these risk factors can be addressed," he says.

Even so, he says, the changeable risk factors "still account for a rather small proportion of the risk,'' probably less than a quarter of cases, he says. Other risk factors are still unknown, he says.

Eventually, the list of risk factors will be even longer, Saade says.

However, he says, some unchangeable risk factors aren't as strong as people may believe.

Even though a woman who has had one stillbirth is at increased risk of another, he says, "the majority of women with a previous stillbirth have a live birth in a subsequent pregnancy."

One major strength of this new study, Saade tells WebMD, is that it looks at an entire population, not just stillbirths from one hospital or one region. This makes the results more valid.