Development of fetal movement--fetal heart rate coupling from 20 weeks through term.

This study documents the development of fetal heart rate (FHR) change in response to fetal movement (FM) in healthy fetuses from 20 weeks' gestational age through term. Thirty-one fetuses received 50 min of Doppler-based monitoring at 20, 24, 28, 32, 36 and 38-39 weeks. FHR and FM were continuously digitized. A coupling index was computed as the percentage of FMs associated with increases in FHR of 5 beats/min or more within -5 or +15 s of movement onset. The latency between FM onset and FHR change was also computed, as were the amplitude and duration of all movements. FM and FHR became more integrated with advancing gestation. Coupling increased and the latency between FM and FHR changes decreased. Maternal age, blood pressure and fetal sex did not affect FM-FHR coupling, but fetuses of women who reported greater stress in their daily lives and had faster heart rates displayed reduced coupling. These data suggest that the development of FM-FHR coupling reflects the development of the central nervous system during gestation, and that development may be affected by maternal factors.