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.