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 .
Effectiveness of Prenatal Vitamin D Deficiency Screening and Treatment Program: A Stratified Randomized Field Trial
Context Despite evidence on the association between hypovitaminosis D and adverse pregnancy outcomes and the positive impact of vitamin D supplementation , no evidence exists supporting a universal screening program in pregnancy as part of routine prenatal care . Objective We sought to determine the effectiveness of a prenatal screening program on optimizing 25-hydroxyvitamin D [ 25(OH)D ] levels and preventing pregnancy complications . Also , to identify a safe regimen , we compared several regimens in a subgroup of vitamin D-deficient pregnant women . Design Two cities of Masjed-Soleyman and Shushtar from Khuzestan province , Iran , were selected as the screening and nonscreening arms , respectively . Within the screening arm , a r and omized controlled trial was conducted on 800 pregnant women . Setting Health centers of Masjed-Soleyman and Shushtar cities . Patients or Participants Pregnant women aged 18 to 40 years . Intervention Women with moderate [ 25(OH)D , 10 to 20 ng/mL ] and severe [ 25(OH)D , < 10 ng/mL ] deficiency were r and omly divided into four subgroups and received vitamin D3 ( D3 ) until delivery . Main Outcome Measure Maternal concentration of 25(OH)D at delivery and rate of pregnancy complications . Results After supplementation , only 2 % of the women in the nonscreening site met the sufficiency level ( > 20 ng/mL ) vs 53 % of the women in the screening site . Adverse pregnancy outcomes , including preeclampsia , gestational diabetes mellitus , and preterm delivery , were decreased by 60 % , 50 % , and 40 % , respectively , in the screening site . A D3 injection in addition to monthly 50,000 IU maintenance therapy contributed the most to achievement of sufficient levels at delivery . Conclusions A prenatal vitamin D screening and treatment program is an effective approach in detecting deficient women , improving 25(OH)D levels , and decreasing pregnancy adverse outcomes
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 .