Can Extreme Stress Cause Birth Defects?
The unexpected death of an older child during the first third of pregnancy when the baby is forming was the situation most likely to be associated with birth defects. When that happened, the risk of abnormalities -- most commonly heart defects and cleft lip or palate -- was more than eight times greater and the risk of other types of birth defects was nearly four times greater
The highest rate of birth defects in women (those who reported unexpected death of a child early in pregnancy) was nearing 5%; for other sudden stressful events it was lower. By comparison, in the group of women unexposed to extreme stress, the rate of birth defects was near 4%, emphasizing that the number of women in either group who had affected babies was small.
Other researchers, such as Carmichael, urge caution in interpreting the study, saying the events defined as stress in the study were severe -- and fortunately, rare -- events. Nonetheless, the study supports the notion that other birth defects that are not caused by genetics or exposure to harmful substances may be stress induced.
Donald R. Mattison, MD, medical director of the March of Dimes in White Plains, N.Y., says some researchers believe there are probably internal "thresholds" above which levels of stress or exposure to other potential dangers can cause damage to a developing fetus. Below those thresholds or levels of stress, however, no damage occurs.
Mattison says the study's finding that more than 95% of women exposed to terribly stressful situations early in pregnancy did not have a baby born with birth defects should be reassuring. And, the finding shows that it is not necessarily the stress itself, but the reaction of the mother's body to the stressful event that is a determining factor.
"Stress is a life experience that is somewhat difficult for us to quantify," Mattison says. He tells WebMD the study's conclusions would be more valuable if researchers could show a link between certain stressful events and specific changes in the mother's body.
"It might be that those individuals at greatest risk of [birth defects] were those that were the most profound responders to stress. It doesn't necessarily have to be a behavioral response, but a biochemical response," Mattison says.