TUESDAY, July 19 (HealthDay News) -- A new study provides evidence that stress from domestic violence during pregnancy may make offspring more prone to stress as an adult.

However, the research doesn't directly prove a cause-and-effect relationship.

It may be difficult to ever prove that stress affecting the bodies of stressed-out pregnant mothers disrupts the inner chemistry of their children. The study does point to the importance of a low-stress pregnancy, however.

"Healthy development starts in the womb, and it is not only nutritional," said study co-author Axel Meyer, an evolutionary biologist at the University of Konstanz in Germany. "Behavioral and emotional factors are important, and the effects are long-lasting."

In recent years, scientists have tried to understand how stress during pregnancy affects the fetus, possibly by altering genes. Research has suggested that anxious and stressed mothers are more likely to have children who develop attention and behavior problems and other issues, said Thomas G. O'Connor, director of the Wynne Center for Family Research at the University of Rochester Medical Center in new York.

It's challenging to figure out whether there's a direct link because many factors other than maternal stress -- such as the environment in which a child is raised -- could explain why kids turn out the way they do.

In science, the gold standard of research is to randomly assign groups of subjects to undergo different treatments or experiences and watch what happens to them. But it would be unethical to expose pregnant mothers to stress. So, researchers examine the effects of stress on pregnant animals, or they try to look backwards to find women who were stressed while pregnant and examine how it may have affected their offspring.

In this study, researchers looked at the genes of women and their children that are thought to be connected to stress.

They found that genetically, mothers stressed by domestic violence appear to "program their offspring to respond in a more costly way when exposed to stressors," Meyer said. The genes in the women themselves weren't affected by exposure to domestic violence.

Meyer said the ongoing stress of the domestic relationships may have been the key problem for the women. "Data from many studies suggest that stressors need not be physical," he said. "Emotional neglect, ongoing familial conflict and other severe forms of adversity may also take their toll."

Could something in the women that makes them more likely to become victims of domestic violence be passed down to their children? Probably not. The researchers linked domestic violence during pregnancy to genetic differences in their children, but they didn't find a link to mothers who experienced domestic violence before pregnancy.

How is the research helpful? "If it really were the case that stress in pregnancy did have persistent effects, then we should invest a great deal more effort and resources in trying to improve well-being in pregnancy," said O'Connor. "It would presumably be cost-effective because you're preventing something from happening."

The study appears in the July 19 issue of Translational Psychiatry.

More information

For more about pregnancy, try the U.S. National Library of Medicine.