High stress during pregnancy is bad news, but it turns out that moderate-stress might boost fetal brain development. Studies in rodents suggest that stress during pregnancy inhibits neural growth, while the children of women who lived in war zones during pregnancy have a higher risk of developing schizophrenia.
To investigate the effects of moderate stress in humans Janet DiPietro and her colleagues at Johns Hopkins University in Baltimore, Maryland, examined 122 healthy pregnant women living in the US three times during their third trimester. They asked the women about their stress levels and recorded fetal movements. They also examined the babies two weeks after birth.
Women who reported higher stress levels during pregnancy had babies that moved around more in the womb. After birth, these babies scored higher on a brain maturation test, although they were more irritable. More active fetuses had better control of body movements after birth. The stress hormone cortisol plays a role in brain maturation, which may help explain the result. (Child Development, vol 8, p115)