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 during pregnancy
Introduction Maternal vitamin D status in pregnancy has been linked to many health outcomes in mother and offspring . A wealth of observational studies have reported on both obstetric outcomes and complications , including pre-eclampsia , gestational diabetes , mode and timing of delivery . Many foetal and childhood outcomes are also linked to vitamin D status , including measures of foetal size , body composition and skeletal mineralization , in addition to later childhood outcomes , such as asthma . Sources of data Synthesis of systematic and narrative review s. Areas of agreement and controversy The findings are generally inconsistent in most areas , and , at present , there is a lack of data from high- quality intervention studies to confirm a causal role for vitamin D in these outcomes . In most areas , the evidence tends towards maternal vitamin D being of overall benefit , but often does not reach statistical significance in meta-analyses . Growing points and areas timely for developing research The most conclusive evidence is in the role of maternal vitamin D supplementation in the prevention of neonatal hypocalcaemia ; as a consequence the UK department of health recommends that pregnant women take 400 IU vitamin D daily . High- quality r and omized placebo-controlled trials , such as the UK-based MAVIDOS trial , will inform the potential efficacy and safety of vitamin D supplementation in pregnancy across a variety of 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 .