Vitamin D Supplementation in Pregnancy and Lactation and Infant Growth

To the Editor: Roth et al. (August 9 issue) 1 report that prenatal and postpartum vitamin D supplementation has no significant effect on the anthropometric measurements of offspring, birth outcomes, or morbidity at 1 year of age. A crucial limitation of the trial, highlighted by the authors, is that supplementation was initiated at 17 to 24 weeks of gestation, even though vitamin D concentrations appear to be most influential much earlier in pregnancy. Increased rates of pregnancy and live birth have been reported for women with elevated serum concentrations of 25-hydroxyvitamin D before conception but not at week 8 of gestation. 2 . . .