Our study has several limitations. Although we attempted to minimize UV light exposure, we can not exclude endogenous vitaminD production.We did not measure the dietary contribution of vitaminD intake,but this should be small compared with supplement doses.We did not include a control group with no maternal cholecalciferol supplementation, because our aim was to determine whether daily supplementation was more advantage ous than a single dose.The limited duration of the study does not allow us to determine the effect of continued cholecalciferol supplementation beyond 28 days or to document long-term safety.