Calcium and phosphorus retention in extremely preterm infants supplemented individually

The aim of this study was to investigate the correlation between the retention of calcium (Ca) and phosphorus (P) and weight gain and intake of Ca and P when using the concept of individualized Ca and P supplementation in extremely low birthweight infants. Three-day Ca and P balances were performed in 20 infants with a mean gestational age of 26.6wk (between 24.1 and 28.7 wk) and a birthweight of 744 g (450-990), when the infant was able to tolerate at least 100 ml/kg/d of milk. The daily supplementation with Ca and P was individually adjusted to achieve a simultaneous excretion of > or = 1.2 mmol/L Ca and > or = 0.4 mmol/L P in the urine. In 16 of the 20 infants, the urinary concentrations of both Ca and P exceeded the lower limits. The retention of Ca (mean 3.8 mmol/kg/d, minimum 0.9; maximum 8.1; 57% of intake, 34-80) and P (2.4,1.1-4.2; 76%, 52-96) was significantly correlated with both the daily weight gain (16 g, 3-28; Ca r2 = 0.22, p = 0.02; P r2 = 0.21, p = 0.03) and the intake of Ca (6.5 mmol/kg/d, 2.4-10.2; r2 = 0.67, p < 0.001) and P (3.1, 1.9-5.3; r2 = 0.85, p < 0.0001). The molar ratio of the Ca and P intake was 2.2 (1.3-4.0).

It was found that Ca and P retention was a function of growth and intake.