Vitamin D Levels and IVF Success
Vitamin D may play various roles in human reproduction and several recently published studies indicate that vitamin D levels are predictive of implantation and ongoing pregnancy rates in in vitro fertilization (IVF).
Vitamin D is really not a “vitamin” but a small family of steroid hormones that increase the absorption of calcium, magnesium, phosphate, iron and zinc from the intestine and which also have effects on many other organ systems. Vitamin D is either consumed, as in certain fortified foods, e.g., dairy products, or synthesized from cholesterol in the skin, when there is sufficient sun exposure. A January 2007 article in the New England Journal of Medicine revealed that the majority of American women may be Vitamin D deficient.
Receptors for Vitamin D are present in the human uterus, ovary and placenta and low levels of vitamin D in pregnancy are associated with pre-eclampsia, gestational diabetes and intrauterine fetal growth retardation. When bound to its receptor, the active form of vitamin D (calcitriol) seems to be involved in estrogen production and implantation. In fact, calcitriol may regulate several genes involved in implantation.
A prospective study of 173 women undergoing IVF in Toronto revealed that women with sufficient vitamin D levels (> 75 nmol/L) had significantly higher pregnancy rates in IVF than women with insufficient levels (>75 nmol/L). Women with sufficient levels had a 52.5% clinical pregnancy rate compared to a 34.7% rate among those with insufficiency. [CMJ Open, 2013 Jun 28;1(2):E77-82]. Another investigation, published inHuman Reproduction, measured vitamin D levels in 388 patients who underwent IVF/ICSI and a single embryo transfer. Clinical pregnancy rates were significantly lower in women with vitamin D levels < 20 ng/ml compared with those with higher concentrations (41 vs. 54%). When controlling for all potentially confounding factors, vitamin D was independently associated with lower clinical pregnancy rates [HumReprod, 2014 Sep;29(9):2032-40].
In a newly published study from Milan, researchers found that women who had sufficient that levels of vitamin D (>20ng/ml) were significantly more likely to produce higher quality embryos and were more like to achieve a clinical pregnancy than women who were vitamin D deficient (<20ng/ml). This prospective study examined 154 women who were vitamin D deficient and 181 women who had sufficient vitamin D blood levels. The clinical pregnancy rates were 20% and 31%, respectively. Interestingly, a subgroup analysis showed that the group of women with the highest levels (>30ng/ml) had the highest chances of pregnancy (J Clin Endocrinol Metab2014 Aug 14:jc2014 1802).
It does appear, then, based upon these and a number of studies between 2005-2010 that Vitamin D plays a key role in human reproduction, maybe involving embryo quality as well as at the uterine lining, where it may facilitate implantation of the embryo. Vitamin D is readily available, inexpensive and has few, if any side effects and may improve one’s fertility potential. However, there are no adequate clinical studies on vitamin D supplementation and IVF outcome.