Vitamin D Deficiency and Infertility

A recent study published in the August, 2014 issue of Clinical Endocrinology and Metabolism, used 20 ng/mL as the cutoff for normal 25-hydroxy-vitamin D levels and considered any level above 20 ng/ml to be normal.  The investigators looked at a group of 335 women preparing to undergo in-vitro fertilization (IVF). The number of women with vitamin D levels below 20 ng/mL was 154, and the number of patients with levels of 20 ng/mL or higher was 181.  The group with the lower vitamin D levels had a clinical pregnancy rate of 20% while the group with the higher levels of vitamin D had a clinical pregnancy rate of 31%.  Additionally, the investigators looked at a subgroup of patients with vitamin D levels of greater than 30 ng/mL and found that this group of patients had the highest chances of pregnancy.

It is important to recognize that vitamin D supplementation was not looked at in this study.  While it is tempting to conclude that supplementing vitamin D to achieve serum levels of 20 ng/mL or higher would improve IVF pregnancy rates, this was clearly not demonstrated in this study.  It is entirely possible that the group of patients whose levels were higher had other factors resulting in improved outcomes such as healthier lifestyles, genetic differences, etc.  Additional studies are needed to confirm a relationship between increased serum vitamin D levels and improved IVF treatment outcomes.  In addition, the question of whether increasing vitamin D levels through supplementation will result in improved IVF success rates has not been answered. This question must be answered by a randomized controlled trial before widespread vitamin D supplementation should be recommended to infertile couples.