Hypocalcemia is a total serum calcium concentration < 8 mg/dL (< 2 mmol/L) in term infants or < 7 mg/dL (< 1.75 mmol/L) in preterm infants. It is also defined as an ionized calcium level < 3.0 to 4.4 mg/dL (< 0.75 to 1.10 mmol/L), depending on the type of electrode used. Signs are primarily neurologic and include hypotonia, apnea, and tetany. Treatment is IV or oral calcium supplementation.
(See also general discussion of hypocalcemia.)
Etiology of Neonatal Hypocalcemia
Neonatal hypocalcemia occurs in 2 forms:
Early onset (in the first 2 days of life)
Late onset (> 3 days), which is rare
Some infants with congenital hypoparathyroidism (eg, caused by DiGeorge syndrome) with agenesis or dysgenesis of the parathyroid glands have both early and late (prolonged) hypocalcemia.
Early-onset hypocalcemia
Risk factors for early-onset hypocalcemia include prematurity, being small for gestational age, maternal diabetes, and perinatal asphyxia. Mechanisms vary.
Normally, parathyroid hormone helps maintain normal calcium levels when the constant infusion of ionized calcium across the placenta is interrupted at birth. A transient, relative hypoparathyroidism may cause hypocalcemia in preterm neonates and some small-for-gestational-age neonates, who have parathyroid glands that do not yet function adequately, and in infants of mothers with diabetes or hyperparathyroidism, because these women have higher-than-normal ionized calcium levels during pregnancy.
Perinatal asphyxia may also increase serum calcitonin, which inhibits calcium release from bone and results in hypocalcemia.
In other neonates, the normal phosphaturic renal response to parathyroid hormone is absent; the elevated phosphate level leads to hypocalcemia.
Late-onset hypocalcemia
The cause of late-onset hypocalcemia is usually ingestion of cow’s milk or formula with a too-high phosphate load; elevated serum phosphate leads to hypocalcemia.
Symptoms and Signs of Neonatal Hypocalcemia
Symptoms and signs of neonatal hypocalcemia rarely occur unless total serum calcium is < 7 mg/dL (< 1.75 mmol/L) or the ionized calcium is < 3.0 mg/dL (< 0.75 mmol/L).
Signs include hypotonia, tachycardia, tachypnea, apnea, poor feeding, jitteriness, tetany, and seizures. Similar signs may occur with hypoglycemia and opioid withdrawal.
Diagnosis of Neonatal Hypocalcemia
Total or ionized serum calcium level
vitamin D metabolite levels.
Treatment of Neonatal Hypocalcemia
Early-onset hypocalcemia ordinarily resolves in a few days, and asymptomatic neonates with serum calcium levels > 7 mg/dL (1.75 mmol/L) or ionized calcium > 3.5 mg/dL (0.88 mmol/L) rarely require treatment. Term infants with levels < 7 mg/dL (1.75 mmol/L) and preterm infants with calcium < 6 mg/dL (<
After acute correction of hypocalcemia, calcium gluconatecalcium gluconate
Late-onset hypocalcemia
Key Points
Neonatal hypocalcemia usually occurs within the first 2 days of life and is most often caused by prematurity, being small for gestational age, maternal diabetes or hyperparathyroidism, and perinatal asphyxia.
Neonates may have hypotonia, tachycardia, tachypnea, apnea, poor feeding, jitteriness, tetany, and/or seizures.
Diagnose by measuring total or ionized serum calcium level; measure glucose level to rule out hypoglycemia.
