To the Editor Brustad et al1 reported offspring 6-year bone health results from a randomized clinical trial of 623 women, who received 2800 IU/d vs 400 IU/d of vitamin D from pregnancy week 24 until 1 week after birth. However, we are concerned about the measurements, data integrity, and the generalizability of the results.
Dual-energy absorptiometry scan data on bone mineral content or bone mineral density (BMC/BMD) were one of the main outcomes; however, the scarcity of baseline measurements at birth or early in infant period may lead to uncertain comparability between groups after 3 and 6 years. If the unethical radiation was concerned in neonates or infants, magnetic resonance imaging2 or quantitative ultrasonography may be used. In addition, the authors did not explain why mothers took vitamin D supplementation until 1 week post partum. If all newborns were fed with breast milk as we assumed, the difference and adjustment of vitamin D dose between fetus (through umbilical cord) and neonates (through milk, with low vitamin D secretion) should be considered carefully.