Rickets in Very Low Birthweight Infants.

Abstract
The influence of extra phosphorus (P) and calcium (Ca) on the incidence of rickets was studied in 40 infants with a birthweight below 1.5 kg. All were fed breastmilk and all received vitamin D 1200 IU/day. Half of the infants were supplemented with P 20 mg/kg/day and Ca 30 mg/kg/day. Rickets, diagnosed with X-ray at 5 to 7 weeks of age, developed in 12 infants, 11 of whom weighed below 1.0 kg. In infants below 1.0 kg rickets was significantly more common in the group not receiving extra P and Ca. After diagnosis all were substituted and radiographic healing occurred in all. Serum Ca concentrations were normal in both groups whereas serum P was significantly lower in non-supplemented patients. Serum alkaline phosphatases (ALP) were normal in all patients at the time of diagnosis demonstrating the risk of using ALP as a diagnostic test for rickets in very low birthweight.