29 Most full-term infants achieve 25-OH-D concentrations of more than 50 nmol/L with vitamin D intakes of 400 IU/day. Backstrom et al 28 found that an intake of 200 IU/kg in the first 6 weeks after birth led to mean 25-OH-D concentrations of ∼50 nmol/L and 80 nmol/L by 12 weeks of age (to convert from nmol/L to ng/mL, divide by 2.5). Calcium and Phosphorus Intake and Absorptionĭata on the relationship between vitamin D intake and serum 25-OH-D in preterm infants are extremely limited. Current data do not support routine use of any of these techniques for preterm infants, including those with abnormal radiographic findings. However, the lack of data related to normal values in former preterm infants indicate that these are performed primarily for research purposes. The use of either bone ultrasonography or, before discharge, dual energy radiographic absorptiometry to evaluate bone status may be considered. Rickets in preterm infants appears radiographically similar to rickets in older infants and should be characterized as such. Nonspecific terms, such as “osteopenia” or “washed out bones,” have little clinical meaning. The radiologist should categorize the infant as likely having or not having rickets. Chest radiographs revealing abnormalities of the ribs may be suggestive of rickets, but a confirmatory long-bone film of the wrist or knee should be obtained to confirm the diagnosis. The ultimate diagnosis of rickets requires a radiographic evaluation, usually of either the wrist or the knee. Approximately 10% to 20% of hospitalized infants with birth weight 1500 g unless there are health issues severely limiting enteral nutrition.

Population-based studies of rickets among preterm infants are lacking therefore, the frequency is not known or reliably estimated.

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