Bruce W Hollis - PhD .Department of Pediatrics Medical University of South Carolina Charleston, SC USA

Pregnancy is a time of tremendous growth and physiological changes for mother and her developing fetus with lifelong implications for the child. The concert of actions that must occur so mother does not reject the foreign tissue of the fetus is substantial. There must be exquisite balance between maternal tolerance to these foreign proteins of paternal origin but also immune surveillance and function such that the mother is not immunocompromised. When this process goes awry, the mother may experience such pregnancy complications as preeclampsia and preterm birth for which there are no preventions or treatments. Vitamin D deficiency affects these processes. Controversy continues with regard to the optimal intake of vitamin D and how to define sufficiency during such vulnerable and critical periods of development. The importance of vitamin D supplementation during pregnancy in preventing some health risks to the mother and fetus appears linked to achieving 25(OH)D concentrations of 40 ng/ml or greater, the beginning of the plateau where conversion of 25(OH)D, the prehormone to 1,25(OH)2D, the active hormone is optimized. Throughout pregnancy, the delivery of adequate vitamin D substrate through sunlight and /or supplement, favorably impacts the epigenome of the fetus, and in turn, long term health. Recent randomized-controlled-trials, both our own and a recent trial performed in Iran by Rostami et al, have demonstrated the dramatic results vitamin D can have on birth outcomes. There is a growing need for future research endeavors to focus not only on critical period(s) from pre-conception through pregnancy, but throughout life to prevent certain epigenetic changes that adversely affect health. The impact of vitamin D and its metabolites on genetic signaling during pregnancy in both mother and fetus is an area of great activity and still in it’s early stages. While vitamin D repletion during pregnancy during pregnancy minimizes the risk of certain adverse outcomes (e.g., preterm birth, asthma, preeclampsia, and gestational diabetes), the mechanisms of how those processes occur are not fully understood. Our current recommendations for supplementing pregnant women is and intake of 4,000 IU/d as early in pregnancy as possible even preconception.