Vitamin D status and supplementation in very preterm infants
Vitamin D plays an important role in bone development and mineralisation, calcium regulation, and immune function. Preterm infants are at high risk of deficiency because they miss the transfer of vitamin D from the mother that normally occurs in late pregnancy. This deficiency can contribute to metabolic bone disease and has also been linked to respiratory complications. Despite this, there is no clear agreement on how much vitamin D preterm infants should receive, with guidelines varying widely, leading to inconsistent clinical practice.
This study looked at vitamin D levels in very preterm infants and how these levels change over time with routine supplementation. Infants born before 32 weeks gestation or with low birth weight were included and grouped based on their total vitamin D intake in the first four weeks of life.
94.3% had vitamin D deficiency
Blood vitamin D levels [25(OH)D] were measured at birth, 4 weeks, and 8 weeks, alongside other clinical markers. The results showed that nearly all infants were deficient at birth. Vit D deficiency defined as 25(OH)D <20ng/mL.
By 4 weeks, deficiency rates were lower in those receiving moderate or higher supplementation (<400, 400-700, or >700IU/kg/day)
By 8 weeks, most infants across all intake groups had reached normal vitamin D levels.
However, higher supplementation was associated with a greater proportion of infants developing excessive levels, while clinical markers remained largely stable and only one infant developed metabolic bone disease.
Overall, the findings indicate that vitamin D deficiency is very common in preterm infants at birth, but standard supplementation can correct this over time.
Lower daily doses appeared sufficient to achieve normal levels while reducing the risk of excessive vitamin D, <400IU/kg generally normalises vitamin D status by 8 weeks.
Higher doses did not show clear additional benefit and increased the likelihood of elevated levels.