The effect of magnesium sulfate on fetal heart rate baseline variability

Variability of the baseline fetal heart rate is correlated with good fetal outcome, and loss of baseline variability has been observed as a sign of fetal distress. Central nervous system depressing drugs may also decrease fetal heart rate variability, and thus recognition of the effect of medication on the baseline fetal heart rate is important for accurate interpretation of fetal monitor tracings. In the cases reported, marked decrease in fetal heart rate variability was observed within 4 minutes of intravenous administration of magnesium sulfate, and fetal outcome was good in all cases.