FETAL SINUS BRADYCARDIA IN THE ABSENCE OF HYPOXIA - A CASE DESCRIPTION OF ALTERATIONS IN FETAL HEART-RATE PATTERN WITH ADVANCING GESTATIONAL-AGE

Objective: The aim of this study was to determine the changes of heart rate pattern in the course of the establishment of fetal sinus bradyc ardia. Methods: Fetal heart monitoring was performed once every week f rom 20 to 37 weeks of gestation. Results: Fetal bradycardia at a rate of 80 beats/min with a total duration of about 5 min during a 30-min r ecording time was initially detected by ultrasound in a fetus at 20 we eks of gestation. At 21 weeks, a baseline heart rate was determined to be 80 beats/min with distinct acceleration. At 22 weeks, sudden but t ransient changes in the baseline fetal heart rate, which ranged from 6 0 to 80 beats/min, were observed and the normal fetal heart rates were recognized as accelerations. After 23 weeks, the baseline fetal heart rate was fixed to be 80 beats/min and sudden changes in the baseline were no longer observed. The amplitude and duration of the acceleratio ns decreased with advancing gestational age. The fetus had no evidence of heart failure during the course of the pregnancy. Conclusions: The serial alterations of heart rate pattern in the development of fetal sinus bradycardia included short-term sinus bradycardia, subsequent pr olongation of the bradycardia, sudden transient changes in the baselin e, and fixation of heart rate as gestational weeks advanced.