Evaluating the Role of Vitamin D3 in Recurrent Miscarriage, a Narrative Systematic Literature Review

The endometrium of RPL women can have abnormal immunological parameters. For successful pregnancy a Th2 response is required, in RM patients there is a baseline autoimmune activation and Th1 immunity. Vitamin D (VD) inhibits Th1 cytokines and stimulates the Th2 phenotype and there is consequently an emerging body of investigation into the relationship between female VD level and RM. The purpose of this review is to evaluate the evidence published associating VD and the success of pregnancy, as well as the therapeutic potential of VD in RM.

Materials and Methods: A literature search was conducted on 8th August 2016 across online bibliographic databases Medline / PubMed, The Cochrane Library, SCOPUS, Web of Science, EMBASE and PROSPERO, based on access of Cambridge University.

Results: Twelf studies were selected as applicable for critical analysis. He following themes were examined:

VD stimulates the Th2 phenotype and deficiency is associated with the abnormalities in RM

VD therapy reduces risk of miscarriage

VD deficiency is prevalent in RM patients

Decreased VDR, but not VD metabolism, is associated with RM

Conclusion: It appears that whilst an inappropriate immune response exists in RM and VD has immunoregulatory roles, there is currently insufficient evidence from the publications reviewed to support either VD deficiency as being a causative factor in RM or the therapeutic benefit of VD in pregnancy outcome. The publications were largely underpowered, inconsistent and, given the difficulty of doing so, failed to control every confounding variable.

Any conclusion that VD is therapeutic in RM assumes the failure of immunological tolerance as the sole cause of RM in otherwise healthy women. Further investigation is therefore required to fully understand the pathogenesis in RM, as well as the mechanism of VD mediated regulation of immunity of pregnancy and the ideal would be for more groups to take on investigating the role of VD in RM.