Meta-analyses of r and omized controlled trials ( RCTs ) document that physiological vitamin D supplementation during pregnancy is safe and improves vitamin D and calcium status , thereby protecting skeletal health .
Although certain RCTs and /or meta-analyses reported some other beneficial effects , it is still not clear whether vitamin D supplementation  improves fertility or decreases the risk of adverse pregnancy outcomes such as low birth weight , pre-eclampsia and neonatal mortality , or reduces wheeze/asthma in the infants .
Vitamin D deficiency is common and there exists a huge gap between recommended dietary vitamin D intakes and the poor vitamin D supply in the general population .
While vitamin D is important for musculoskeletal health , there are accumulating data suggesting that vitamin D may also be important for fertility , pregnancy outcomes and lactation .
Significant changes in vitamin D metabolism during pregnancy such as increased production of the " active vitamin D hormone " calcitriol support the important role of vitamin D in this setting .
Observational studies show that vitamin D deficiency is a risk marker for reduced fertility and various adverse pregnancy outcomes and is associated with a low vitamin D content of breast milk .
Nevertheless , vitamin D supplementation in pregnant women is frequently required to achieve a sufficient vitamin D status as recommended by nutritional vitamin D guidelines .
Effects of Maternal Vitamin D Supplementation on the Maternal and Infant Epigenome.
INTRODUCTION Mothers and infants are at high risk for inadequate vitamin D status . Mechanisms by which vitamin D may affect maternal and infant DNA methylation are poorly understood . OBJECTIVE This study quantified the effects of vitamin D3 supplementation on DNA methylation in pregnant and lactating women and their breastfed infants . MATERIAL S AND METHODS In this r and omized controlled pilot study , pregnant women received vitamin D3 400 international units ( IU ) ( n = 6 ; control ) or 3,800 IU ( n = 7 ; intervention ) daily from late second trimester through 4 - 6 weeks postpartum . Epigenome-wide DNA methylation was quantified in leukocytes collected from mothers at birth and mother-infant dyads at 4 - 6 weeks postpartum . RESULTS At birth , intervention group mothers showed DNA methylation gain and loss at 76 and 89 cytosine-guanine ( CpG ) dinucleotides , respectively , compared to controls . Postpartum , methylation gain was noted at 200 and loss at 102 CpGs . Associated gene clusters showed strongest biologic relevance for cell migration/motility and cellular membrane function at birth and cadherin signaling and immune function at postpartum . Breastfed 4 - 6-week-old infants of intervention mothers showed DNA methylation gain and loss in 217 and 213 CpGs , respectively , compared to controls . Genes showing differential methylation mapped most strongly to collagen metabolic processes and regulation of apoptosis . CONCLUSIONS Maternal vitamin D supplementation during pregnancy and lactation alters DNA methylation in mothers and breastfed infants . Additional work is needed to fully eluci date the short- and long-term biologic effects of vitamin D supplementation at varying doses , which could hold important implication s for establishing clinical recommendations for prenatal and offspring health promotion
Meta-analyses of r and omized controlled trials ( RCTs ) document that physiological vitamin D supplementation during pregnancy is safe and improves vitamin D and calcium status , thereby protecting skeletal health .
Although certain RCTs and /or meta-analyses reported some other beneficial effects , it is still not clear whether vitamin D supplementation  improves fertility or decreases the risk of adverse pregnancy outcomes such as low birth weight , pre-eclampsia and neonatal mortality , or reduces wheeze/asthma in the infants .
Vitamin D deficiency is common and there exists a huge gap between recommended dietary vitamin D intakes and the poor vitamin D supply in the general population .
While vitamin D is important for musculoskeletal health , there are accumulating data suggesting that vitamin D may also be important for fertility , pregnancy outcomes and lactation .
Significant changes in vitamin D metabolism during pregnancy such as increased production of the " active vitamin D hormone " calcitriol support the important role of vitamin D in this setting .
Observational studies show that vitamin D deficiency is a risk marker for reduced fertility and various adverse pregnancy outcomes and is associated with a low vitamin D content of breast milk .
Nevertheless , vitamin D supplementation in pregnant women is frequently required to achieve a sufficient vitamin D status as recommended by nutritional vitamin D guidelines .