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 .
Response to Antenatal Cholecalciferol Supplementation Is Associated With Common Vitamin D–Related Genetic Variants
Context : Single-nucleotide polymorphisms ( SNPs ) in genes related to vitamin D metabolism have been associated with serum 25-hydroxyvitamin D [ 25(OH)D ] concentration , but these relationships have not been examined following antenatal cholecalciferol supplementation . Objective : To determine whether SNPs in DHCR7 , CYP2R1 , CYP24A1 , and GC are associated with the response to gestational cholecalciferol supplementation . Design : Within-r and omization group analysis of the Maternal Vitamin D Osteoporosis Study trial of antenatal cholecalciferol supplementation . Setting : Hospital antenatal clinics . Participants : In total , 682 women of white ethnicity ( 351 placebo , 331 cholecalciferol ) were included . SNPs at rs12785878 ( DHCR7 ) , rs10741657 ( CYP2R1 ) , rs6013897 ( CYP24A1 ) , and rs2282679 ( GC ) were genotyped . Interventions : 1000 IU/d cholecalciferol from 14 weeks of gestation until delivery . Main Outcome Measure : 25(OH)D at r and omization and 34 weeks of gestation were measured in a single batch ( Liaison ; Diasorin , Dartford , UK ) . Associations between 25(OH)D and the SNPs were assessed by linear regression using an additive model [ β represents the change in 25(OH)D per additional common allele ] . Results : Only rs12785878 ( DHCR7 ) was associated with baseline 25(OH)D [ β = 3.1 nmol/L ; 95 % confidence interval ( CI ) , 1.0 to 5.2 nmol/L ; P < 0.004 ] . In contrast , rs10741657 ( CYP2R1 ) ( β = −5.2 nmol/L ; 95 % CI , −8.2 to −2.2 nmol/L ; P = 0.001 ) and rs2282679 ( GC ) ( β = 4.2 nmol/L ; 95 % CI , 0.9 to 7.5 nmol/L ; P = 0.01 ) were associated with achieved 25(OH)D status following supplementation , whereas rs12785878 and rs6013897 ( CYP24A1 ) were not . Conclusions : Genetic variation in DHCR7 , which encodes 7-dehyrocholesterol reductase in the epidermal vitamin D bio synthesis pathway , appears to modify baseline 25(OH)D. In contrast , the response to antenatal cholecalciferol supplementation was associated with SNPs in CYP2R1 , which may alter 25-hydroxylase activity , and GC , which may affect vitamin D binding protein synthesis or metabolite affinity
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 .