Hypomagnesemia in infants of diabetic mothers: perinatal studies.

Fifty-six diabetic mothers and their infants were studied prospectively from birth. Twenty-one of 56 IDM had serum Mg less than or equal to 1.5 mg/dl, on at least one occasion during the first 3 days. Serum Mg in these hypomagnesemic infants did not demonstrate the normal increase with postnatal age that was present in normomagnesemic infants. Decreased neonatal serum Mg was related to increased severity of maternal diabetes, young mothers, mothers for lower gravidity, and prematurity. Decreased serum Mg, alone or with decreased ionized or total Ca, did not correlate with neuromuscular irritability in the infants. Decreased serum Mg in IDM was associated with decreased maternal serum Mg, decreased neonatal ionized and total Ca, increased serum P, and decreased parathyroid function. Serum Mg was not related to dietary P intake, or urinary Ca or P excretion. Thus, transitory neonatal hypomagnesemia occurs in IDM; it is speculated that factors causing HM might include maternal HM or neonatal hyperphosphatemia, and that the HM is related to the hypocalcemia and functional hypoparathyroidism of IDM.