[Prevention of bone mineral deficiency in premature infants: review of the literature with focus on monitoring of urinary calcium and phosphate]

Abstract

Background: Bone mineral deficiency of prematurity (BMDoP) is caused by the lack of simultaneous availability of calcium (Ca) and anorganic phosphate (P) during rapid skeletal growth.

Methods: Review of the literature on the prevention of BMDoP, with specific attention to the limitations of the monitoring of urinary calcium and phosphate concentrations.

Results: Intrauterine bone mineral accretion (BMA) can be achieved in preterm infants if urinary concentrations of Ca and P continuously show that the supplementation with these ions slightly exceeds the actual need. An individually adjusted supplementation with Ca and P appears rational because both growth velocity and enteral Ca absorption are highly variable and determine the need for enteral Ca and P administration. If, however, urinary concentrations of Ca and P are used to determine whether Ca and P supplementation is adequate, mechanisms affecting the urinary excretion of these ions other than nutrition have to be taken into account. Specifically, methylxanthines and diuretics increase the renal Ca losses, and the renal P threshold may be lowered in premature infants. A positive effect of physical activity on BMA has been shown in several studies.

Conclusions: An individualized Ca and P supplementation in preterm infants aiming for supplementation in a slight excess of the actual need and guided by urinary Ca and P concentrations appears able to prevent BMDoP. Monitoring of urinary Ca and P concentrations needs to take into account non-nutritional factors affecting these concentrations. BMA may further be improved by physical activity.