THE EFFECT OF MAGNESIUM-SULFATE THERAPY ON THE DURATION OF LABOR IN WOMEN WITH MILD PREECLAMPSIA AT TERM - A RANDOMIZED, DOUBLE-BLIND, PLACEBO-CONTROLLED TRIAL

OBJECTIVE: The primary outcome was to determine whether magnesium sulf ate therapy prolongs the duration of labor in women with mild preeclam psia. Secondary outcomes were to assess the side effects associated wi th magnesium sulfate therapy: hours and maximum dose of oxytocin, inci dence of progression to severe preeclampsia, incidence of cesarean del ivery, change in maternal hematocrit, incidence of postpartum hemorrha ge, incidence of maternal infection, and Apgar scores. STUDY DESIGN: W omen with a diagnosis of mild preeclampsia at term were randomized to receive standard therapy during labor and for 12 hours post partum wit h either magnesium sulfate (n = 67) or a matching placebo solution (n = 68). RESULTS: There was no difference between magnesium sulfate and placebo with respect to the primary outcome variables: total length of labor (median 17.8 hours vs 16.5 hours, p = 0.7) and length of the ac tive phase of labor (median 5.4 hours vs 6.0 hours, p = 0.5). In addit ion, no difference was observed in the secondary outcome variables: ho urs of oxytocin use, change in hematocrit, frequency of maternal infec tion, progression to severe preeclampsia, incidence of cesarean delive ry, and Apgar scores. Although not statistically significant, the inci dence of postpartum hemorrhage was approximately fourfold greater in t he magnesium sulfate group (relative risk 4.1, 95% confidence interval 0.5 to 35.4). There was a significant difference in the maximum dose of oxytocin used (13.9 +/- 8.6 mU/min with magnesium sulfate vs 11.0 /- 7.6 mU/min with placebo, p = 0.036). CONCLUSION: The use of magnesi um sulfate during labor in women with mild preeclampsia at term does n ot affect any component of labor but did necessitate a higher dose of oxytocin.