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 vitamin D supplementation to improve the vitamin D status of breast-fed infants: a randomized controlled trial.
OBJECTIVE To determine whether a single monthly supplement is as effective as a daily maternal supplement in increasing breast milk vitamin D to achieve vitamin D sufficiency in their infants . PATIENTS AND METHODS Forty mothers with exclusively breast-fed infants were r and omized to receive oral cholecalciferol ( vitamin D3 ) 5000 IU/d for 28 days or 150,000 IU once . Maternal serum , breast milk , and urine were collected on days 0 , 1 , 3 , 7 , 14 , and 28 ; infant serum was obtained on days 0 and 28 . Enrollment occurred between January 7 , 2011 , and July 29 , 2011 . RESULTS In mothers given daily cholecalciferol , concentrations of serum and breast milk cholecalciferol attained steady levels of 18 and 8 ng/mL , respectively , from day 3 through 28 . In mothers given the single dose , serum and breast milk cholecalciferol peaked at 160 and 40 ng/mL , respectively , at day 1 before rapidly declining . Maternal milk and serum cholecalciferol concentrations were related ( r=0.87 ) . Infant mean serum 25-hydroxyvitamin D concentration increased from 17±13 to 39±6 ng/mL in the single-dose group and from 16±12 to 39±12 ng/mL in the daily-dose group ( P=.88 ) . All infants achieved serum 25-hydroxyvitamin D concentrations of more than 20 ng/mL. CONCLUSION Either single-dose or daily-dose cholecalciferol supplementation of mothers provided breast milk concentrations that result in vitamin D sufficiency in breast-fed infants . CLINICAL TRIAL REGISTRATION clinical trials.gov NCT01240265
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 .