In the past 18 months, I have written 3 blogs on Vitamin D and fertility:

Vitamin D & IVF – What’s New 2013

Can Vitamin D Influence Fertility?

Does Vitamin D Matter? Recent Studies on Vitamin D and Fertility

It’s time for another update. Let’s look at what new information is available.

In June 2014, Researchers from Belgium reported in Human Reproduction their findings on Vitamin D levels drawn 7 days before embryo transfer. All women in the study had a single Day 5 blastocyst embryo (SET) transferred. The study was a retrospective review including 368 patients.

Their findings:

• 65% of the women had a deficient 25-OH Vitamin D level (< 20 ng/ml).
• Clinical pregnancy rates were significantly lower in women who were Vitamin D deficient (41 versus 54%). Live- birth rates were also lower in the Vitamin D deficient group.
• Interestingly, pregnancy rates were the same in women with Vitamin D levels of 20-30 (insufficient) and > 30 (sufficient).
• Using logistic regression analysis of 16 factors, Vitamin D deficiency was independently associated with lower clinical pregnancy rates. The vast majority of the patients in this study were Caucasian.

A second study was published in the February 2014 edition of Fertility and Sterility. 25-OH Vitamin D levels were obtained prior to embryo transfer in egg donor recipients. Embryo transfers were performed on Days 3 or 5 with a mean number of embryos transferred of 2.5.

The authors observed:

• In this retrospective cohort study of 99 egg donation recipients, only 35% had a 25-OH Vitamin D  > 30 ng/mL (38% were insufficient and 26% deficient).
• Significantly higher clinical pregnancy rates (78% vs. 37%) and live-birth rates (59% vs. 31%) were observed in patients with 25-OH Vitamin D levels  > 30 ng/mL.
• The authors propose that their observed lower pregnancy rates in patients with 25-OH Vitamin D levels <30 ng/mL was likely due to localized effects on the endometrium.

These 2 studies continue to add to our increasing understanding of the potential role of Vitamin D and human reproduction. As in prior reports, patients with low 25-OH vitamin D levels appear to have lower clinical pregnancy and live-birth rates. There is also increasing evidence that Vitamin D deficiency is associated with adverse pregnancy outcomes. .

To date, there are still no prospective studies yet published demonstrating that Vitamin D supplementation in women with insufficient or deficient levels will result in an increase in the live -birth rate. Such studies are needed and will greatly aid our understanding of Vitamin D and fertility.

Conclusions:

1. In all women attempting pregnancy, especially those undergoing IVF; consider measuring a 25-OH Vitamin D level.

2. In those women who are found insufficient or deficient, Vitamin D supplementation should be utilized.

3. The ideal 25-OH Vitamin D level has yet to be defined. Levels of at least 20 ng/mL appear to be beneficial.

5. Typical supplementation doses are 2000-4000 IU of Vitamin D3 daily.

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