PHENYTOIN AND MAGNESIUM-SULFATE EFFECTS ON FETAL HEART-RATE TRACINGS ASSESSED BY COMPUTER-ANALYSIS

Objective: To compare the effects of maternally administered phenytoin and magnesium sulfate on the fetal heart rate (FHR) using computer an alysis. Methods: Thirty-six nonlaboring preeclamptic women between 27- 41 weeks' gestation were treated with either phenytoin or magnesium su lfate in a nonrandomized fashion. All fetuses were deemed to be welt b y traditional electronic-biophysical criteria. One-hour FHR recordings were analyzed by computer analysis before treatment. No other medicat ions were administered. Tracings recorded 1 hour after drug administra tion were analyzed. Therapeutic serum levels were achieved in both gro ups before FHR tracings were reevaluated. Statistical analysis used pa ired Student t test, with significance set at P less-than-or-equal-to .05. Results: There were no differences in birth weight, gestational a ge, Apgar scores, or computer-analyzed FHR characteristics between the groups before treatment. Magnesium sulfate reduced significantly the frequency of accelerations of ten and 15 beats per minute; caused a 62 % reduction in reactivity, defined as accelerations of 15 beats per mi nute in 20 minutes of FHR tracing (but no change in reactivity with ac celerations of ten beats per minute); and reduced short-and long-term variability. Phenytoin reduced short-term variability only. Conclusion : Phenytoin does not confound the computer analysis of FHR tracings an d may offer some advantage over magnesium sulfate when used for prophy laxis against eclampsia.