Is vitamin D deficiency linked with infertility?

A prospective Italian study published in The Journal of Clinical Endocrinology & Metabolism suggests that low levels of vitamin D [25(OH)D] may contribute to infertility. The finding, which the authors acknowledge does not confirm causality, could point to possible therapeutic benefits of the vitamin in women undergoing in vitro fertilization (IVF).

In the cross-sectional study, the success of IVF was evaluated in 335 women-154 who were deficient in 25 (OH)D and 181 with adequate 25 (OH)D levels-who had been referred to the Infertility Unit of the Fondazione Ca’ Granda at Ospedale Maggiore Policlinico in Milan for IVF in 2012. Inclusion criteria were an indication for IVF, age 18 to 42, body mass index 18 to 25 kg/m², and adequate ovarian reserve.

Serum samples for 25(OH)D measurement were taken at the time of cycle preparation and patients were excluded if an IVF cycle was cancelled or excessively delayed. A 25(OH)D level ≤20 ng/mL was considered deficient and ≥20 ng/mL was considered sufficient.

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The clinical pregnancy rate was 20% (30/154) among the women with 25(OH)D deficiency, compared with 31% in (56/181) in those with sufficient 25(OH)D (P=0.02; adjusted odds ratio for clinical pregnancy in women with vitamin D ≥20 ng/mL 2.15 [95% CI: 1.23=3.77]).

In a press release, author Alessio Paffoni, MSc, noted that this is “the largest study to date to examine how vitamin D affects fertility in women who are undergoing IVF.  “Although randomized clinical trials are needed to confirm the findings, our results certainly suggest that low levels of vitamin D contribute to infertility.”  

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