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 .
Maternal Versus Infant Vitamin D Supplementation During Lactation: A Randomized Controlled Trial
OBJECTIVE : Compare effectiveness of maternal vitamin D3 supplementation with 6400 IU per day alone to maternal and infant supplementation with 400 IU per day . METHODS : Exclusively lactating women living in Charleston , SC , or Rochester , NY , at 4 to 6 weeks postpartum were r and omized to either 400 , 2400 , or 6400 IU vitamin D3/day for 6 months . Breastfeeding infants in 400 IU group received oral 400 IU vitamin D3/day ; infants in 2400 and 6400 IU groups received 0 IU/day ( placebo ) . Vitamin D deficiency was defined as 25-hydroxy-vitamin D ( 25(OH)D ) < 50 nmol/L. 2400 IU group ended in 2009 as greater infant deficiency occurred . Maternal serum vitamin D , 25(OH)D , calcium , and phosphorus concentrations and urinary calcium/creatinine ratios were measured at baseline then monthly , and infant blood parameters were measured at baseline and months 4 and 7 . RESULTS : Of the 334 mother-infant pairs in 400 IU and 6400 IU groups at enrollment , 216 ( 64.7 % ) were still breastfeeding at visit 1 ; 148 ( 44.3 % ) continued full breastfeeding to 4 months and 95 ( 28.4 % ) to 7 months . Vitamin D deficiency in breastfeeding infants was greatly affected by race . Compared with 400 IU vitamin D3 per day , 6400 IU/day safely and significantly increased maternal vitamin D and 25(OH)D from baseline ( P < .0001 ) . Compared with breastfeeding infant 25(OH)D in the 400 IU group receiving supplement , infants in the 6400 IU group whose mothers only received supplement did not differ . CONCLUSIONS : Maternal vitamin D supplementation with 6400 IU/day safely supplies breast milk with adequate vitamin D to satisfy her nursing infant ’s requirement and offers an alternate strategy to direct infant supplementation
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 .