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390: Adverse neonatal effects of magnesium sulfate given to the mother

      Objective

      Given the increasing indications for administration of magnesium sulfate to pregnant women, we sought to determine if such therapy was associated with adverse effects in the newborn infant.

      Study Design

      This is a retrospective cohort analysis of women who received magnesium sulfate for prevention of eclampsia. Magnesium sulfate was given intravenously beginning with a 6 gram loading dose followed by 2-3 gram/hour based on serum magnesium levels. Newborn hypotonia was diagnosed if at birth the infant exhibited less than normal tone/activity unresponsive to naloxone and persistent at admission to the nursery. Maternal serum magnesium levels were measured within four hours of delivery. Women undergoing general anesthesia were excluded.

      Results

      Between January 2000 and February 2009, 6827 women with preeclampsia were treated with magnesium sulfate as described and 388 (5.7%) infants were diagnosed to have hypotonia. There was a direct relationship between maternal magnesium levels and hypotonia and this persisted after correction for gestational age and umbilical artery pH (Figure 1). A similar adjusted analysis was also performed for intubation in the delivery room and magnesium concentration in maternal blood was significantly associated with intubation.

      Conclusion

      The concentration of magnesium in maternal blood is directly related to hypotonia in the newborn infant as well as the need for intubation of the infant at birth.