Recent research has shown that fetuses may participate in maternal relaxation, and that guided imagery is linked to increased fetal well-being at the time of relaxation.

The study, “Fetal response to abbreviated relaxation techniques: A randomized controlled study,” involved 33 mothers and their fetuses. The average age of the mothers involved in this study was 33 years. Each woman was between weeks 32 and 34 of her pregnancy, with a single, healthy fetus.

The women in the study were randomly assigned to one of three groups: the control group, the progressive muscle relaxation group or the guided imagery group. Women in the control group experienced 10 minutes of quiet rest in a semi-recumbent position. Women in the progressive muscle relaxation and guided imagery groups experienced 10 minutes of their assigned intervention in the same semi-recumbent position.

Prior to these interventions, researchers took baseline samples and measurements of each participant’s cortisol and norepinephrine levels, blood pressure and heart rate. These same samples and measurements were taken again immediately after the 10-minute relaxation period, then again 10 minutes later and a final time 10 minutes after that.

Throughout the entire study period, researchers monitored the mothers’ fetuses for fetal heart rate, including average short- and long-term variations in fetal heart rate, as well as fetal heart rate acceleration. Uterine activity and fetal body movements were also monitored.

“Generally, high long-term variation and high short-term variation of the [fetal heart rate] indicate good fetal condition,” state the study’s authors.

Results of the research revealed no significant differences among the three groups in terms of fetal behavioral states, fetal heart rate or fetal body movements throughout the study period.

However, the two intervention groups did have higher long-term variation of fetal heart rate during and 10 minutes after relaxation, as compared to the control group. Fetuses of mothers in the guided imagery group showed a trend toward higher short-term fetal heart rate than the fetuses of mothers in the progressive relaxation group. Additionally, more fetal heart rate acceleration could be seen among the fetuses in the control group as compared to the two intervention groups.

In regards to uterine activity, women in the progressive muscle relaxation group had significantly more uterine activity during all measured time points than women in the guided imagery or control groups. No associations were found between fetal behaviors and maternal heart rate, blood pressure, cortisol and norepinephrine level.

“Fetuses of mothers in the intervention groups had higher [fetal heart rate] long-term variation, which was especially seen during and 10 minutes after relaxation,” state the study’s authors. “These findings could imply the effectiveness of [progressive muscle relaxation and guided imagery].

“In addition, there were more [fetal heart rate] accelerations seen in control group fetuses, which could have been caused by more activity compared to fetuses in the intervention groups,” they added.

The researchers also warned against progressive muscle relaxation for women with a tendency toward high perception of body sensations, because the potential increased uterine activity could lead to “unnecessary worries or even anxiety in these women.”

Authors: Nadine S. Fink, Corinne Urech, Fornaro Isabel, Andrea Meyer, Irène Hoesli, Johannes Bitzer and Judith Alder.

Sources: Department of Developmental Pediatrics, Children’s Hospital Boston, Harvard Medical School, Boston, Massachusetts; Department of Obstetrics and Gynecology, Department of Applied Statistics in Life Sciences, University Hospital Basel, Switzerland. Originally published in Early Human Development (2010).