PHYSIOLOGY OF ISOLATED LONG-TERM VARIABILITY OF THE FETAL HEART-RATE

Ten singleton third trimester fetuses exhibiting isolated long-term va riability of the fetal heart rate were studied with a single Doppler t ransducer actocardiograph in conjunction with real-time ultrasonograph y. Each of these studies revealed repetitive clustered bursts of fetal breathing movements during the acceleratory phases and apneic episode s during the deceleratory phases of this fetal heart rate pattern, res pectively, in the absence of other fetal movements. This observation m ay explain the physiology of isolated long-term variability of the fet al heart rate.