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432: The association of magnesium sulfate with maternal morbidity when used for preeclampsia without severe features

      Objective

      Current recommendations, based on low quality evidence, suggest avoiding magnesium sulfate (MgSO 4) in women who have preeclampsia (PreE) without severe features. Yet, since more than half of women who experience an eclamptic seizure have no prior severe features, practitioners often use MgSO4. We aimed to quantify the risk of adverse outcomes associated with MgSO4 in women without severe features of PreE.

      Study Design

      This was a secondary analysis of an observational cohort of 115,502 mother/infant dyads who delivered at 25 U.S. hospitals, Mar 2008 to Feb 2011. Included were women with PreE without severe features at any time in pregnancy, per local hospital standards, and who delivered after 32 weeks gestation (to exclude MgSO4 use for CP prophylaxis). Our primary outcome was a composite of severe maternal morbidity: postpartum hemorrhage (PPH), pulmonary edema, intensive care unit (ICU) admissions or death. Secondary outcomes included cesarean, use of any uterotonic beyond oxytocin, MgSO4 toxicity requiring calcium gluconate, neonatal ICU admission and perinatal death. PPH was defined by an EBL ≥ 1500 mL at delivery or the immediate postpartum period, a blood transfusion, or a hysterectomy for hemorrhage or atony. Comparisons were made based on the administration of of MgSO4 anytime during the delivery hospitalization. Multivariable logistic regression was used to adjust for confounding.

      Results

      Of the women in the initial cohort, 2,468 (2.1%) met inclusion criteria. The groups differed by maternal race, insurance status, tobacco/drug use and gestational age at birth. The crude and adjusted odds ratios (OR) are in Table. The frequency of composite maternal morbidity was significantly higher in women who received MgSO4 (8.6%) compared with those who did not (3.9%; aOR 2.1). Those who received MgSO4 had 4-fold higher odds of ICU admission (aOR 4.2) and were more likely to require additional uterotonics (aOR 1.6). Neonatal outcomes were similar. Magnesium toxicity occurred in 7 women (0.5%). Results were similar after adjustment for hospital.

      Conclusion

      When MgSO4 is used in preeclampsia without severe features, it is associated with an increased risk of severe maternal morbidity.
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