Vitamin D supplementation alone may reduce risk of gestational diabetes, among other pregnancy complications

Supplementing pregnant women with vitamin D alone may reduce the risk of gestational diabetes, pre‐eclampsia, low birth weight and among other pregnancy complications, revealed a latest study published in the Cochrane Library.

Vitamin D is essential for human health, particularly bone, muscle contraction, nerve conduction, and general cellular function. Low concentrations of blood vitamin D in pregnant women have been associated with pregnancy complications. It is thought that additional vitamin D through supplementation during pregnancy might be needed to protect against pregnancy complications. However, it is not clear if vitamin D supplementation, alone or in combination with calcium or other vitamins and minerals, during pregnancy has benefits or harms to the mother or her offspring.

Cristina Palacios, a professor in the Department of Dietetics and Nutrition, at the Robert Stempel College of Public Health & Social Work, has been studying the effects of vitamin D supplementation during pregnancy for more than a decade. In her most recent review, she and her team evaluated the effect of supplementation with vitamin D alone or in combination with other micronutrients for women during pregnancy in comparison to placebo or no intervention, irrespective of dose, duration or time of commencement of supplementation or type of supplementation (oral or by injection).

Two review authors independently i) assessed the eligibility of trials against the inclusion criteria, ii) extracted data from included trials, and iii) assessed the risk of bias of the included trials. The certainty of the evidence was assessed using the GRADE approach.

Key results

• Supplementation with vitamin D alone during pregnancy probably reduces the risk of pre‐eclampsia, gestational diabetes, probably reduces the risk of having a baby with low birth weight compared to women who received placebo or no intervention.


• Vitamin D supplementation may make little or no difference in the risk of having a preterm birth < 37 weeks compared to no intervention or placebo.


• In terms of maternal adverse events, vitamin D supplementation may reduce the risk of severe postpartum hemorrhage.


• There were no cases of hypercalcemia


• whether vitamin D increases or decreases the risk of nephrotic syndrome was uncertain

Based on their results, the authors concluded that vitamin D supplementation alone may reduce the risk of pre‐eclampsia, gestational diabetes, low birth weight and further may reduce the risk of severe postpartum hemorrhage. Supplementing pregnant women with vitamin D and calcium probably reduces the risk of pre‐eclampsia but may increase the risk of preterm births < 37 weeks (these findings warrant further research).