Vitamin D and parathormone levels of late-preterm formula fed infants during the first year of life

Background/Objectives: Preterm infants are at risk for low vitamin D but documentation on late-preterm infants is sparse. This prospective study monitored longitudinally vitamin D and parathormone (PTH) levels in late-preterm formula fed infants during the first year of life, taking into consideration in utero and postnatal growth, and season and diet. Subjects/Methods: The study population comprised 128 infants of gestational age (GA) 32-36 weeks, of which 102 were appropriate (AGA) and the remaining 26 were small for GA (SGA). Serum levels of vitamin D (25(OH)D), PTH calcium, phosphate (P) and alkaline phosphate were estimated at 2 and 6 weeks, and at 3, 6, 9 and 12 months of age. Results: The 25(OH)D levels were relatively low at 2 and 6 weeks in both AGA and SGA infants (21 +/- 11, 20 +/- 7 ng/ml and 25 +/- 16, 23 +/- 8 ng/ml, respectively), but increased at 6 months (45 +/- 14, 47 +/- 10 ng/ml) and remained stable thereafter. SGA infants had lower 25(OH)D levels at 9 and 12 months (AGA 45 +/- 14, 47 +/- 18 ng/ml vs SGA 38 +/- 13, 37 +/- 13 ng/ml, P<0.05). Deficiency of 25(OH)D (<20 ng/ml) was found in 18.5% of measurements in 92 (72%) infants, and its insufficiency (20-32 ng/ml) was found in 29.2% of measurements in 99 (77.3%) infants. Most measurements with vitamin D <32 ng/ml were observed at the first three study points, where PTH showed an inverse association with 25(OH)D, reaching a plateau thereafter. Conclusions: Late-preterm, formula fed infants may have suboptimal vitamin D levels and elevated PTH, especially, during the first 3 months. Those born SGA may have lower vitamin D levels up to the end of the first year of life. European journal of Clinical Nutrition (2012) 66, 224-230; doi:10.1038/ejcn.2011.158; published online 7 September 2011