Mom’s Cortisol Linked to Low Birth Weight

The stress hormone cortisol may be a potential mechanism for transmitting a U.S. mother’s stress to her unborn baby and contributing to low birth weight.

Maternal distress is accompanied by biochemical changes, such as increased cortisol, that can both directly and indirectly affect the fetus, said Miguel A. Diego, a psychobiologist at the University of Miami School of Medicine.

Cortisol can directly cross through the placenta into the fetus, which could affect fetal development.

The study, in the September-October issue of Psychosomatic Medicine, found the fetuses of mothers who show high rates of depression, anxiety and stress weigh less and are smaller than average at midterm.

Cortisol can also affect the mother’s vascular function, thereby reducing blood flow to the fetus, which could affect fetal growth by diminishing the amount of oxygen and nutrients that are delivered, according to Diego.

After analyzing the effects of demographics, maternal distress and hormonal levels on 98 women, the researchers found prenatal cortisol was the only significant predictor of fetal weight.