The effects of maternally administered magnesium sulfate on the neonate.

The effects of parenterally administered magnesium sulfate on maternal and neonatal calcium and magnesium metabolism in nonasphyxiated, term pregnancies complicated by pregnancy-induced hypertension were studied prospectively. In addition, the neurobehavioral effects of neonatal hypermagnesemia were investigated by means of a neonatal assessment scale that specifically measures reflex activity and both passive and active muscle tone. Maternal magnesium sulfate infusion was associated with maternal and neonatal hypermagnesemia when compared with that of control subjects (1.8 +/- 0.10 to 3.6 +/- 0.5 mg/dl, p less than 0.001, and 1.75 +/- 0.2 to 3.6 +/- 0.5 mg/dl, p less than 0.005, respectively). Maternal serum calcium levels fell with magnesium therapy (9.3 +/- 0.18 to 7.9 +/- 0.1 mg/dl, p less than 0.001), while neonatal calcium levels were unaffected (10.8 +/- 0.44 to 10.5 +/- 0.38 mg/dl, p less than 0.05). Neurological status examinations in the neonate were similar in both the control and treatment groups. In addition, neurological performance of the neonate did not correlate with cord magnesium levels or to the total dose of magnesium administered.