Selective magnesium sulfate prophylaxis for the prevention of eclampsia in women with gestational hypertension

OBJECTIVE: To describe the incidence of eclampsia in women with mild gestational hypertension when only women with severe gestational hypertension are given magnesium sulfate prophylaxis. METHODS: This is a prospective 4(1)/(2)-year observational study. Those women who met our criteria for severe gestational hypertension received intravenous magnesium sulfate prophylaxis, and women with nonsevere hypertension did not. Data were collected at delivery to ascertain the incidence of eclampsia and maternal and neonatal morbidity. RESULTS: A total of 72,004 women were delivered during the study period, 6,431 had gestational hypertension, 3,935 met the criteria for severe disease and were given magnesium sulfate prophylaxis, 2,496 women with nonsevere hypertension were not treated. Eighty-seven women developed eclampsia, for an overall incidence of 1 in 828 deliveries, a 50% increase when compared with 5 preceding years where all women with gestational hypertension were given magnesium sulfate prophylaxis. Of the 2,496 women with nonsevere hypertension who were not treated, 27 had eclampsia (1 in 92). Women with eclampsia were more likely to require general anesthesia for cesarean delivery compared with hypertensive women without eclampsia (23% versus 4%, P <.001), but they had no additional morbidity. Infants of eclamptic mothers had more adverse outcomes than those without convulsions (12% versus 1%, P <.04). CONCLUSION: Selective magnesium sulfate prophylaxis results in an increased overall incidence of eclampsia because of more seizures in women with nonsevere gestational hypertension who are not given magnesium sulfate prophylaxis.