Researchers from Boston Children’s Hospital (Harvard Medical School) examined whether maternal relaxation exercises impact fetal behavior and uterine activity, while also investigating the underlying physiological and endocrine mechanisms for the transfer of relaxation from mother to fetus.

The behavior of 33 fetuses was analyzed during laboratory relaxation/quiet rest and controlled for baseline fetal behavior.  Potential associations between relaxation/quiet rest and fetal behavior (fetal heart rate, fetal heart rate variation, fetal heart rate acceleration, and body movements) and uterine activity were studied, using a computerized cardiotocogram system. Maternal heart rate, blood pressure, cortisol, and norepinephrine levels were all measured.

Two interventions, progressive muscle relaxation and guided imagery, showed changes in fetal behavior.  The intervention groups had higher long-term variation during and after relaxation compared to the controls (p=.039), and the control fetuses had more fetal heart rate acceleration, especially during and after quiet rest (p=.027).

Women in the progressive muscle relaxation group had significantly more uterine activity than women in the guided imagery group (p=.011) and than the women controls. Maternal heart rate, blood pressure, and stress hormones were not associated with fetal behavior.

This study concludes that the fetus might participate in maternal relaxation and suggests that guided imagery is superior to progressive muscle relaxation. This could especially be true for women who tend to direct their attention to body sensations such as abdominal activity.

Citation:  Fink NS, Urech C, Isabel F, Meyer A, Hoesli I, Bitzer J, Alder J. Fetal response to abbreviated relaxation techniques. A randomized controlled study. Early Human Development. 2010 Dec 23. [Epub ahead of print]