Objective: Hypocalcemia is common in infants of diabetic mothers (IDMs) and may be caused by secondary hypoparathyroidism related to hypomagnesemia. This study was designed to test the hypothesis that prophylactic magnesium sulfate (MgSO4) administration at birth in IDMs with low cord magnesium concentrations will prevent neonatal hypocalcemia.
Study design: In this randomized trial conducted in IDMs with a cord magnesium concentration of <0.74 mM (1.8 mg/dl), 26 subjects received 6 mg/kg elemental magnesium and 23 subjects received no treatment. Serum concentrations of total and ionized calcium, phosphorus, and magnesium were recorded at birth, by measuring the concentrations within the umbilical cord, and at 24 and 72 hours of age.
Results: The incidence of hypocalcemia at 72 hours was 0% (0 of 23) in the magnesium-treated group and 12.5% (2 of 16) in the group with no treatment (p = 0.16). There was no difference in mean serum calcium concentration at 72 hours between infants in the treated group and the group with no treatment (2.28 +/- 0.04 vs 2.22 +/- 0.05 mM; p = 0.39). The drop in serum calcium concentration from birth to 72 hours of age was less for the treated group (0.30 +/- 0.05 mM [1.23 +/- 0.18 mg/dl]) than the group with no treatment (0.45 +/- 0.05 mM [1.81 +/- 0.21 mg/dl]; p = 0.04).
Conclusion: Administration of intramuscular MgSO4 to IDMs with cord magnesium <0.74 mM (1.8 mg/dl) does not reduce the incidence of hypocalcemia in infants of well-controlled diabetic mothers.