Relaxation exercises such as guided imagery [GI] may help both the expectant mother and the growing fetus to relax, according to a study published in Early Human Development (2011; 87, 121–27). Pregnancy-associated stress can influence fetal growth and gestation length, and can promote prematurity and low birth weight. This study’s purpose was to investigate whether a fetus could participate momentarily in maternal relaxation and, if so, to determine the underlying mechanisms responsible for the transferral. Since many expectant mothers are reluctant to take medications, mind-body interventions are a well-accepted alternative.
Researchers analyzed data from 33 pregnant women who were, on average, in their 32nd week of pregnancy and who were randomly assigned to either a relaxation intervention or a control group. Intervention group members participated in either progressive muscle relaxation [PMR] or GI. Investigators measured maternal heart rate, blood pressure and stress hormone levels before the relaxation intervention, immediately after it, 10 minutes later and then 10 minutes later again. Fetal behavior—including fetal heart rate [FHR], heart rate variation, heart rate acceleration, body movements and uterine activity—was monitored at similar intervals.
Data analysis showed that fetuses of mothers in both relaxation intervention groups had greater long-term variation in FHR, while fetuses in the control group had more FHR acceleration. A high level of FHR variation is associated with fetal well-being. FHR acceleration may be caused by more fetal activity. Comparing differences between fetuses in the GI and the PMR interventions, researchers found that fetuses in the GI group had higher FHR variation. Women in the PMR group had more uterine activity.
Lead study author Nadine Fink, of the Children’s Hospital Boston and Harvard Medical School, said, “The key point is that the fetus is able to relax in response to maternal relaxation. These are preliminary findings and need to be replicated first in order to make this conclusion. It seems like mothers and fetuses prefer the ‘more passive’ form of relaxation, the guided imagination, whereas the progressive muscle relaxation is activating.”
The study authors recommended that more research be done with larger sample sizes that would be more representative of the general population of pregnant women.