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Vitamin D may reduce the frequency of spontaneous abortion

Posted on: November 8, 2016   by  Amber Tovey


A randomized controlled trial published in the Global Journal of Health Science found daily vitamin D supplementation reduced the frequency of spontaneous abortion.

Recurrent spontaneous abortion (RSA) refers to when a woman experiences at least two consecutive or three non-consecutive pregnancy miscarriages before 20 weeks of gestation. Approximately 2 – 5% of women of reproductive age are affected by this condition. RSA can cause physical and mental stress among families, as well as a heavy economic burden.

While researchers have proposed various causes of RSA, the exact cause remains unknown. Some researchers hypothesize that the RSA may result from a disruption of immunomodulation. Furthermore, studies have illustrated that women who suffer from RSA have high levels of interleukin-23 (IL-23) and T helper cell-17 (Th17); both of which play a role in increasing inflammation.

Due to the well-established anti-inflammatory properties of vitamin D, researchers recently conducted a randomized controlled trial to evaluate the effects of vitamin D supplementation among women with RSA who had visited the hospital for pre-pregnancy checkups.

A total of 80 patients with RSA were enrolled in the study. The women were divided into two groups, a vitamin D group and a placebo group. The vitamin D group received 400 IU of vitamin D3 daily, and the placebo group received a dummy pill daily. Vitamin D levels were evaluated at the 10th and 20th weeks.

The researchers wanted to determine whether the vitamin D group would experience fewer spontaneous abortions than the placebo group. Furthermore, the researchers measured IL-23 levels among all patients involved in the study to evaluate the effects of vitamin D supplementation on this pro-inflammatory cytokine. Here is what the researchers found:

  • The vitamin D status at baseline was 11.7 ng/ml in the vitamin D group and 11.5 ng/ml in the placebo group at baseline.
  • At the end of the study, vitamin D levels were 13.2 ng/ml and 11.1 ng/ml in the vitamin D group and placebo group, respectively (p = 0.004).
  • At the end of the study, the IL-23 levels increased in the placebo group, and decreased in the vitamin D group (p < 0.001).
  • A total of 5 and 13 spontaneous abortions occurred in the intervention and placebo groups, respectively (p = 0.03).

After adjusting for confounding factors, such as age, number of previous abortions and serum levels of IL-23, the effect of vitamin D on the incidence of abortion did not remain statistically significant. However, the relationship between the IL-23 levels and the incidence of abortion was significant (p < 0.001). This implies that vitamin D3 influences spontaneous abortion frequency through its modulation of IL-23.

The researchers concluded,

“Results of the study showed that the administration of vitamin D3 in women with [RSA] can reduce the level of IL-23 and subsequently the incidence of abortion.”

Unfortunately, the study used a meager 400 IU vitamin D supplement daily, which begs the question of whether adequate daily doses of vitamin D (near 5000 IU) would elicit more profound effects on the incidence of spontaneous abortion. Regardless of the small dose, the RCT produced promising findings, which will hopefully lead to further trials investigating the role of vitamin D in the prevention of spontaneous abortions and miscarriages.


Tovey, A. Vitamin D may reduce the frequency of spontaneous abortion. The Vitamin D Council Blog & Newsletter, 2016.


Samimi, M. et al. Effect of Vitamin D Supplementation on Unexplained Recurrent Spontaneous Abortion: A Double-Blind Randomized Controlled Trial. Global Journal of Health, 2016.

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