In pregnant women, especially during the first phases, the role of vitamin D appears to be mainly immunomodulatory, rather than – more traditionally – a calcium-regulating factor, although this function does retain its importance.
Interestingly, vitamin D inadequacy in the early stages of pregnancy could be an instance of the “Barker Hypothesis”. According to this theory, certain diseases in adults might have their roots in nutrient insults experienced in the perinatal period (either in utero and/or during the early months of life).
Still today there is little agreement on the optimal vitamin D dosages to be utilized as supplementation during pregnancy.