Doppler of the umbilical and fetal middle cerebral arteries after magnesium sulfate in preeclampsia

Abstract

BACKGROUND. To compare the ratio between the fetal middle cerebral artery and the umbilical artery using Doppler flow velocimetry indices (resistance index, pulsatility index and A/B relation) before and after administration of magnesium sulfate to pregnant women with severe preeclampsia (pure or superimposed). METHODS. A prospective cohort study was conducted with each pregnant woman representing her own control. Forty severe preeclamptic women were included and underwent Doppler sonography before and 20 minutes after administration of 6g of magnesium sulfate. Analysis variables were the Doppler flow velocimetry indices evaluating the ratio of the fetal middle cerebral artery to the umbilical artery. To compare the mean indices before and after magnesium sulfate for the same patient, the "t-paired" Student test was used. The Stuart-Maxwellχ2 was applied to determine the difference of fetal diagnosis (normal, brain-sparing or reduced middle cerebral artery resistance) before and after magnesium sulfate. RESULTS. No significant difference of the mean ratio between the middle cerebral artery and the umbilical artery, before and after administration of magnesium sulfate was observed. After magnesium sulfate (25.0% x 47.5%; p = 0.01), there was an increased frequency of isolated lower Doppler flow velocimetry indices in the middle cerebral artery. CONCLUSION. Intravenous administration of magnesium sulfate in patients with severe preeclampsia is associated with increased frequency of fetal Doppler diagnosis of reduced resistance in the middle cerebral artery.