Magnesium Status in Infancy

Abstract

The magnesium levels at birth (indicated by cord levels) reflect the fetal response to maternal conditions during gestation: systemic and placental, and the ease or difficulty of delivery with resultant normal or hypoxic state of the newborn infant. Conditions that lead to neonatal hypermagnesemia might mask an underlying magnesium deficiency. Hypermagnesemia might result from administration of pharmacologic doses of magnesium to the mother shortly before delivery for management of toxemia of pregnancy, or from egress of magnesium from the tissues of infants subjected to anoxia, acidosis, or surgery. Exchange transfusions with citrated blood profoundly affect magnesium as well as calcium homeostasis. Levels during the first week of life reflect the infant’s adjustment to independent life in the absence of immediate maternal blood-borne factors, and are affected by the nature of milk and supplements provided. The nature of feeding also influences levels later in infancy. Metabolic abnormalities that interfere with magnesium absorption or retention, although not common, have produced severe mineral imbalances that have focused pediatricians’ attention on magnesium. More common conditions, such as severe diarrhea and intestinal malabsorption syndromes, which also cause hypo-magnesemia, have further stimulated the pediatrician to be alert to magnesium loss. This section calls attention to the conditions and mechanisms that make infants susceptible to magnesium deficiency and presents speculations as to possible late, as well as overt, immediate sequellae.