Khatiwada A, Wolf BJ, Mulligan JK, et al. - For the second aim of the Kellogg Foundation grant, reserachers conducted this double-blind RCT examining how plasma vitamin D metabolite 25-hydroxyvitamin D (25(OH)D) affect plasma immune-mediators during pregnancy. They enrolled and randomized pregnant women at 10–14 weeks gestation to receive 400 or 4,400 IU vitamin D₃/day. At each trimester, they gathered data on health, safety, circulating 25(OH)D, and 9 immune-mediators. Increased 25(OH)D was observed at second and third trimesters in both treatment groups; it was greatest in the 4,400 IU group. Though there were associations between baseline 25(OH)D and baseline TGF-β and second and third trimester IFN-β and IL-2, no impact was observed of vitamin D supplementation throughout pregnancy on immune-mediators at later trimesters. Conceivable influences on immune-mediator responses during pregnancy could be seen in correlation with supplementing with vitamin D before conception.