Vitamin D fortification improves chances of live birth in infertile women

A margarine fortification programme that exposes infertile women to extra vitamin D leads to better odds of live birth, a study has found.

The study included 16,212 women diagnosed with infertility. Researchers used data from the mandatory vitamin D fortification of margarine in Denmark, which was terminated in 1985. The termination served as a cutoff point to divide the study population into the following exposure groups: 1) the vitamin D–exposed group (women who had their primary infertility diagnosis in the fortification period; n=6,313); 2) a washout-period group (women with a primary infertility diagnosis in 1985–1986; n=1,404); 3) a vitamin D–nonexposed group (women diagnosed with primary infertility in 1986–1991; n=8,495).

Chances of a live birth within 12 months after diagnosis were higher in the exposed group (odds ratio [OR], 1.87, 95 percent confidence interval [CI], 1.68–2.08) relative to the nonexposed group. In the washout group, the estimate was somewhat lower compared to that in the exposed group although still better than in the nonexposed group (OR, 1.52, 95 percent CI, 1.27–1.81)

Estimates or overall risk patterns were similar in analyses covering a longer follow-up (15–18 months after infertility diagnosis) and restricted to women with anovulatory infertility. There was a little seasonal variation when calendar period of conception was applied.

The present data support the hypothesis that sufficient vitamin D levels help increase the chances of live birth in infertile women, according to the researchers. Additional studies are warranted to establish the potential biologic mechanisms linking vitamin D to chance of live birth in infertile women, as well as to determine who may benefit from supplementation with vitamin D and what the optimal dose is for those in need of supplementation.