ABSTRACT
The effect of magnesium sulfate (MgSO4) in intrapartum fetal behavior as judged by heart rate cycl icity was investigated by comparing the fetal heart characteristics of 15 term fetuses whose mothers received MgSO4 with a control group of 54 healthy term fetuses whose mothers received noantepartum medications. The duration of different fetal heart cycles and percentage of time spent in a particular cycle except for cycle C (6 to 10 beats per minute) were not different between groups. Seventy-seven percent of fetuses of the study group versus 24% of fetuses in the control group exhibited markedly diminished variability (cycle A) and 8% versus 63%, respectively, experienced cycles of increased variability (cycle D). Our observations may explain the conflicting conclusions of previous reports regarding the affect of MgSO4 on fetal heart rate variability.
