Fetal responses to induced maternal relaxation during pregnancy

Abstract

Fetal responses to induced maternal relaxation during the 32nd week of pregnancy were recorded in 100 maternal-fetal pairs using a digitized data collection system. The 18-min guided imagery relaxation manipulation generated significant changes in maternal heart rate, skin conductance, respiration period, and respiratory sinus arrhythmia. Significant alterations in fetal neurobehavior were observed, including decreased fetal heart rate (FHR), increased FHR variability, suppression of fetal motor activity (FM), and increased FM-FHR coupling. Attribution of the two fetal cardiac responses to the guided imagery procedure itself, as opposed to simple rest or recumbency, is tempered by the observed pattern of response. Evaluation of correspondence between changes within individual maternal-fetal pairs revealed significant associations between maternal autonomic measures and fetal cardiac patterns, lower umbilical and uterine artery resistance and increased FHR variability, and declining salivary cortisol and FM activity. Potential mechanisms that may mediate the observed results are discussed.

Figure 1

Although fetal heart rate (bpm) changed significantly over time, F (2,194) = 3.07, p < .05, the change between segments was limited to the baseline to relaxation periods for the group without a pre-baseline period only, F (1, 56) = 12.03, ***p < .001. Unlike other figures, significance notation here refers to this group only.

Figure 2

Fetal heart rate variability (bpm) showed linear increase over time, F (2, 194) = 5.81, p < .01, but change between segments was focused on the baseline period to relaxation, F (1,98) = 8.65, **p < .01.

Figure 3

Fetal movement (arbitrary units) suppression was displayed during the relaxation period with return to baseline levels following the recovery period; this pattern was unaffected by pre-baseline condition. ***p < .0001.

Figure 4

Fetal FM-FHR coupling was augmented during the relaxation period and returned to baseline levels following the recovery period; this pattern was unaffected by pre-baseline condition. **p < .01. ***p < .001.