Many Americans, for example, believe maternal thoughts and actions contribute to adverse fetal outcomes, says Jonathan Schaffir, a clinical assistant professor of obstetrics and gynecology at Ohio State University.
"I think it's kind of amazing that people out there still believe that a pregnant woman seeing something frightening could cause her baby to have a birthmark. That was an 18th-century belief and it's still circulating," he says online in the journal Archives of Women's Mental Health.
Most miscarriages result from genetic or chromosomal abnormalities in the fetus, or from medical complications relating to hormonal imbalances or problems with the uterus or placenta, Schaffir added.
More than a third of 200 women surveyed by Schaffir said a pregnant woman's foul mood could negatively affect her baby.
One in four thought a pregnant woman's exposure to upsetting situations could hurt her unborn child, and one in five believed excessive exercise could cause a woman to miscarry.
"In general, minor day-to-day experiences don't have an effect on whether a pregnancy is successful or not," he said, adding exceptions include the abuse of alcohol or drugs during pregnancy, which can lead to complications.
