Osteopenia in preterm infants

The placenta converts vitamin D to 1,25-dihydrocholecalciferol which enables phosphate to be transported across the placenta. 3 A reduced ability to do so explains the higher incidence of postnatal rickets that may be seen in infants with intrauterine growth restriction suggesting that chronic injury to the placenta may limit the ability to transfer phosphate. 4 Poor mineralisation may also occur in pre-eclampsia and chorioamnionitis. 5 6 Many infants born prematurely develop significant problems that require treatment, and the therapies required such as steroids, methylxanthines and diuretics may have a significant detrimental effect on bone mineralisation. 7 - 9 In addition, postnatal nutrition is often significantly suboptimal, further affecting bone mineralisation and supplementation is often needed, but may be difficult to achieve. There is limited availability of this technology however, and this, combined with the size of the scanner, the length of time needed to complete a scan and movement artefact (technically possible does not mean that the procedure is free of technical difficulties) have meant that there has been relatively restricted use in preterm and term infants, although there has been enough use in a research environment to permit validation of the technique. 19 The data that are available have supported the use of DEXA scans in preterm and term infants as an aid to diagnosing and monitoring metabolic bone disease of prematurity but have also confirmed that artefact induced by a baby's spontaneous movement can substantially decrease precision. 20 If this technique were to be adopted as a routine method of screening for either the risk or the presence of metabolic bone disease, issues of availability would need to be resolved and agreement would need to be reached on practical questions including the timing of the initial scan, the frequency with which scans should be repeated, the point at which intervention would be offered and what intervention, if any, would be appropriate.\n Urinary calcium and phosphate creatinine ratios Variations in urinary calcium and phosphate concentrations are well recognised, and simultaneous measurement of creatinine may allow correction for changes in urine volume.