Study Suggests Maternal Stress And Stress Hormones May Influence Fetal Brain Development In Utero

Although maternal factors such a stress and stress hormones have been shown to play a significant role in pregnancy outcomes related to prematurity, their influence on fetal brain development is not well understood, Wadhwa said. However, in this most recent study, research was conducted to examine whether features of the maternal environment were associated with measures of fetal brain function.

An experimental measure of fetal brain function was developed by quantifying fetal heart rate responses to a series of external stimuli using an instrument that produces both sound and vibration similar to an electric toothbrush. This instrument routinely is used by obstetricians in clinical practice to awaken a sleeping fetus. The study sample was comprised of 156 mother-fetus pairs at 33 weeks gestation.

Maternal assessments included interviews and questionnaires to assess psychosocial and behavioral factors such as stress, maternal blood samples for bioassays of maternal and placental stress hormones and medical records to obtain information related to obstetric risk factors.

The study results indicated fetuses exhibited a significant and sustained increase in heart rate responses to the vibroacoustic challenge protocol. There were marked individual differences in the pattern of fetal responses to the instrument, Wadhwa said. Characteristics of the challenge protocol, such as the number of stimuli and time interval between successive stimuli, were associated with the overall pattern of fetal responses. After adjusting for these effects, maternal factors related to medical, endocrine, psychosocial and behavioral stress significantly were associated with the overall pattern of fetal responses.

The magnitude of the fetal responses to challenge was greater in women with medical problems, high levels of stress hormones, high levels of psychological stress, and low levels of social support, according to the study. The study is among the first to suggest that factors related to medical, endocrine and psychosocial stress during human pregnancy may negatively impact fetal brain development and function, as evidenced by their relationship with measures of fetal reactivity and learning. The effects of early environment on development are believed to be like those of a double-edged sword, wherein optimal environments may produce beneficial effects, and hostile environments, such as that effected by prenatal stress, may produce detrimental effects on brain development.

Researchers now are involved in new studies at the University of Kentucky and the University of California to further clarify the effects of maternal stress during pregnancy on fetal as well as infant brain and other developmental and health outcomes.