Disorders of maternal calcium metabolism implicated by abnormal calcium metabolism in the neonate.

Normal fetal and neonatal calcium homeostasis is dependent upon an adequate supply of calcium from maternal sources. Both maternal hypercalcemia and hypocalcemia can cause metabolic bone disease or disorders of calcium homeostasis in neonates. Maternal hypercalcemia can suppress fetal parathyroid function and cause neonatal hypocalcemia. Conversely, maternal hypocalcemia can stimulate fetal parathyroid tissue causing bone demineralization. We report two asymptomatic women, one with previously unrecognized hypoparathyroidism and the other with unrecognized familial benign hypercalcemia, who were diagnosed when their newborn infants presented with abnormalities of calcium metabolism. J.B. was born at 34 weeks' gestation with transient hyperbilirubinemia and thrombocytopenia. At 1 month of age he had severe bone demineralization, cortical irregularities, widening and cupping of the metaphyses, and lucent bands in the scapulae. The total serum calcium and phosphorus were normal with an ionized calcium of 5.4 mg/dL (4.6-5.4). His alkaline phosphatase, parathyroid hormone, and 1,25-dihydroxyvitamin D levels were all increased. P.B., mother of J.B., had no symptoms of hypocalcemia either prior to, or during this pregnancy. She had severe hypocalcemia and hyperphosphatemia, laboratory values typical of hypoparathyroidism. J.N. presented at 6 weeks of age with new onset of seizures and tetany secondary to severe hypocalcemia. The serum phosphorus, creatinine, alkaline phosphatase, and parathyroid hormone levels were normal. At 15 weeks of age his calcium was slightly elevated with a low fractional excretion of calcium. P.N., mother of J.N., had no symptoms of hypercalcemia either prior to, or during this pregnancy. Her serum calcium was 12.7 mg/dL and urine calcium was 66.5 mg/24 hr, with a low fractional excretion of calcium ranging from 0.0064 to 0.0073. P.N. has a brother who previously had parathyroid surgery. Both J.N. and P.N. meet the diagnostic criteria for familial benign hypercalcemia. These cases illustrate the important relationships between maternal serum calcium levels and neonatal calcium homeostasis. They emphasize the need to assess maternal calcium levels when infants are born with abnormal serum calcium levels or metabolic bone disease.