Enamel defects were commoner in preterm children, and post-natal dietary intervention had no effect on their frequency. This is the first study in which enamel defects in both primary and permanent teeth have been studied in the same group of preterm children. At age 1 and 2 yrs, 32 preterm children were examined, and the same group was examined again at 9-11 yrs. As controls, 106 healthy children were examined at 1 and 2 yrs, and 64 of them were randomly selected for comparison. When the preterm children were aged 9-11 yrs, 64 of another group of 150 10-13 yr-olds were randomly chosen as controls. All were examined by the main author. At 2 yrs, 66% of preterm children had enamel hypoplasia, and 2% of controls (P < 0.001); enamel opacity affected respectively 13% and 19% (NS). However, the proportions of teeth thus affected were respectively 16% and 0.1%, and 13% and 4%. In the permanent dentition around 10 yrs later, 38% of preterm children had hypoplasia, and 11% of controls (P < 0.01), and opacity affected respectively 47% and 25% (P < 0.05). All preterm infants had primary dentition enamel defects, and 72% also had permanent dentition defects. The preterm infants had been randomly assigned to 2 levels of vitamin D supplementa-tion up to age 6 months, and to breast milk with or without a supplement of calcium and phosphorus until reaching a weight of 2kg. These supplements had no apparent effect on enamel defects.

Aims-To test the hypothesis that a vitamin D dose of 200 IU/kg, maximum 400 IU/day, given to preterm infants will maintain normal vitamin D status and will result in as high a bone mineral density as that attained with the recommended dose of 960 IU/day. Methods-Thirty nine infants of fewer than 33 weeks of gestational age were randomly allocated to receive vitamin D 200 IU/kg of body weight/day up to a maximum of 400 IU/day or 960 IU/day until 3 months old. Vitamin D metabolites, bone mineral content and density were determined by dual energy x-ray absorptiometry, and plasma ionised calcium, plasma alkaline phosphatase, and intact parahormone measurements were used to evaluate outcomes. Results-The 25 hydroxy vitamin D concentrations tended to be higher in infants receiving 960 IU/day, but the diVerences did not reach significance at any age. There was no diVerence between the infants receiving low or high vitamin D dose in bone mineral content nor in bone mineral density at 3 and 6 months corrected age, even after taking potential risk factors into account. Conclusions-A vitamin D dose of 200 IU/kg of body weight/day up to a maximum of 400 IU/day maintains normal vitamin D status and as good a bone mineral accretion as the previously recommended higher dose of 960 IU/day. Vitamin D is a potent hormone which aVects organs other than bone and should not be given in excess to preterm infants.

Metabolic bone disease is recognized with increasing frequency in very-low-birth-weight infants. Radiological changes characteristic of rickets have been found in 55% of infants with a birth weight of less than 1000 g and in 23% of infants weighing less than 1500 g at birth. Twenty-four per cent of infants with a birth weight of less than 1500 g have fractures. The main aetiological factor is insufficient phosphorus supplementation. The aetiology is, however, multifactorial and also includes calcium deficiency, vitamin D deficiency, certain drugs, aluminium loading and immobilisation. The method of choice in detecting subclinical mineral bone disease of prematurity is measurement of bone mineral density, but there is as yet no single good diagnostic method available for premature infants. The optimal mineral and vitamin D requirement of the premature infant must be established so that proper recommendations can be given. The current recommended vitamin D dose in Europe (ESPGAN 800-1000 IU/day) is probably too high when extra minerals are supplied. Moreover, the duration of mineral supplementation may need to be continued until the infant has reached a body weight of 3.5 kg. This article deals with the aetiology, pathogenesis, diagnosis and future prospects of metabolic bone disease of prematurity.

The short-term benefit to bone mineral density in preterm infants of mineral supplementation of the early diet is obvious, but, in the long term, the effects seem to disappear. The results also imply that a relatively long period of breast-feeding may be needed to optimize long-term bone mineral acquisition in the lumbar spine.