Metabolic bone disease in preterm infants.

Small preterm infants often develop osteopenia with or without rickets and with or without fractures. Whether these bone abnormalities all form part of the same disease process with a wide spectrum of presentation or whether each abnormality represents a different disease is as yet unclear. Bone mineralization depends largely on adequate supplies of calcium and phosphate. The normal intra-uterine accretion of these minerals is higher than can be achieved by feeding preterm babies postnatally with breastmilk or conventional formulas. Supplementation with calcium, phosphorus and vitamin D is needed to prevent the development of 'neonatal osteopathy'. The main action of vitamin D in the preterm baby is probably to increase the intestinal absorption of calcium and phosphorous, although it may, together with other calciotrophic hormones, have a more specific effect on bone growth.