Pregnant mother’s stress may slow baby’s growth in the womb.

A new study shows that pregnant women under extreme stress have smaller fetuses in mid-pregnancy than expectant mothers who are not distressed.

Dr. Miguel A. Diego and colleagues found that cortisol – the hormone released by the adrenal gland in times of stress – appears to be the responsible factor.

Diego said that women with clinical depression or anxiety disorders who are under heavy stress should seek medical treatment, adding that the mother's psychological state has an effect on fetal development.

There is evidence linking pregnant women's distress to premature birth and low birth weight, but no studies have directly looked at how stress during pregnancy may affect the fetus before birth. To investigate this, Diego and colleagues performed ultrasound exams on 98 women who were all between 16 and 29 weeks pregnant, checked their hormone levels, and had them complete tests to evaluate their anxiety and stress levels.

The more depression, anxiety, and daily stress a woman faced, the smaller her fetus, according to the researchers. A statistical analysis revealed that higher cortisol levels were directly linked to higher levels of stress and lower estimated fetal weight.

Diego noted that controversy continues about the safety of antidepressants during pregnancy, and said other means of helping distressed pregnant women could include psychotherapy or more social support.

The results of the study are reported in the journal Psychosomatic Medicine .

SOURCES: Miguel A. Diego, University of Miami School of Medicine, Miami, FL, USA. Psychosomatic Medicine, September-October 2006.