Women who face significant financial, emotional or other personal stresses in the year before they give birth may be at increased risk of stillbirth, according to a new National Institutes of Health study.
Recent data estimates that there is one stillbirth for every 167 births in the U.S. Though doctors and researchers have identified many factors that increase women's risk -- including smoking during pregnancy, severe high blood pressure and placental problems -- much is still unknown as to the causes of stillbirths, defined as the death of a fetus at 20 weeks or more.
In the new study, published in the American Journal of Epidemiology this week, researchers interviewed 2,000 women at 59 U.S. hospitals immediately after they gave birth to a healthy baby or had a stillbirth. Eighty three percent of the women who had a stillbirth said they had experienced a stressful life event in the past year, as did 75 percent of the women who had a normal delivery.
But the study also found that the more stressful the life event that a woman experienced, the higher her risk of stillbirth. Women who faced five or more stressful life events were 2.5 times more likely to have a stillbirth as compared to women who reported no major events in the preceding year.
The stressors researchers asked about included things like losing a job, moving, homelessness, the death or illness of a close friend or family member, separation or divorce or arguing with a husband or partner more than usual. Certain stressors were more closely tied to stillbirth risk than others: Women who had been in a physical fight or had heard their partners say they did not want the baby had the highest risk of stillbirth, as did women who had been in prison in the past year or whose partners had.
Prior studies have also tied psychological stress to stillbirth. A 2008 investigation from Denmark found that women who experienced high levels of stress throughout their pregnancy had an 80 percent increased risk of having a stillbirth, although their overall risk remained relatively small. That study, as well as the new one, is part of a growing body of research that has linked psychological stress during pregnancy to outcomes such as premature birth and low birth weight.
Study author Marian Willinger, chief of the pregnancy and perinatology branch of the Eunice Kennedy Shriver National Institute of Child Health and Human Development -- one of two NIH entities that funded the research -- told The Huffington Post that experts still have a long way to go in understanding the link between stress and stillbirth.
One possibility is that stress activates certain pathways in the neuroendocrine system, releasing hormones that have been implicated in preterm labor and, possibly, stillbirth, she said. Stress might also make women prone to infection, which the March of Dimes says causes between 10 and 25 percent of stillbirths; or there may be other biological pathways that are not yet understood, Willinger added.
It is also possible that non-biological factors are at play. The researchers controlled for certain socioeconomic risk factors, like marital status and income, but they did not measure women's access to medical care or the quality of that care, both of which can affect pregnancy outcomes. Additionally, researchers asked only whether women had experienced a difficult event in the past year; they did not ask them to describe how stressful they had found the event, or how they had coped with it.
"This is where we need to do more research," Willinger said. "We need to understand this better."
In the meantime, she said that the new findings are not meant to frighten women or make them feel worried about the possible effects of stressful live events that are beyond their control, emphasizing that the overall risks are relatively small.
"Women who have multiple stressors in their lives are more likely to have a loss," Willinger said. "So it's important that their clinician be aware of what's going on in their lives and that they try to get as much support as they can to diminish the stressor and help deal with it."