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 .
The Effects of Vitamin D Supplement on Prevention of Recurrence of Preeclampsia in Pregnant Women with a History of Preeclampsia
Introduction Preeclampsia is a pregnancy-specific syndrome . One of the hypotheses concerning the etiology of preeclampsia is vitamin D deficiency during pregnancy . Method and Material s The present study is a r and omized controlled clinical trial which aims to determine the effect of vitamin D supplement on reducing the probability of recurrent preeclampsia .  72 patients were placed in control group while 70 patients were r and omized to the intervention group . The intervention group received a 50000 IU pearl vitamin D3 once every two weeks . The control group was administered placebo . Vitamin D or placebo was given until the 36th week of pregnancy . Results The patients in intervention group have significantly lower ( P value = 0.036 ) probability of preeclampsia than patients in the control group . The risk of preeclampsia for the control group was 1.94 times higher than that for the intervention group ( 95 % CI 1.02 , 3.71 ) . Conclusion The intended intervention ( i.e. , prescription of vitamin D ) has a protective effect against recurrent preeclampsia .  Vitamin D supplementation therapy in pregnancy could help in reducing the incidence of gestational hypertension/preeclampsia . Registration This study has been registered in Iranian Registry of Clinical Trials ( I RCT ) site with ID number I RCT 2017010131695N1
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 .