Can Vitamin D Influence Fertility?

Dr. Sgarlata

By Dr. Carmelo Sgarlata, a board-certified reproductive endocrinologist with extensive experience in the field of in vitro fertilization and integrative medicine and head of ORM’s Integrative Medicine practice.

Vitamin D deficiency has been associated with a number of fertility problems, including PCOS, endometriosis, uterine fibroids, abnormal sperm function and reduced IVF success. Adverse pregnancy outcomes including preterm birth, gestational diabetes and preeclampsia have been observed in women with vitamin D Deficiency. Vitamin D is also important for normal bone health and immune function.

What is a Normal Vitamin D level? A quick review

  • To assess Vitamin D, a blood sample is taken and the 25 (OH) Vitamin D level is measured. Using the current Endocrine Society classification:
  • Adequate (replete): 30 ng/ml or greater.
  • Insufficient: 21 to 29 ng/ml.
  • Deficient: below 20 ng/ml
  • Factors that contribute to vitamin D deficiency include inadequate dietary intake, dark skin, aging, obesity, geographic location, and sun exposure.
  • The current RDA for Vitamin D is 600 IU.
  • Keep in mind, a newborn baby’s vitamin D levels is largely dependent on the maternal vitamin D status. Those of us who live in the Pacific Northwest are at greater risk for vitamin D deficiency or insufficiency (geographic location and sunlight exposure).

What is the ideal vitamin D level for fertility and successful pregnancy?

A recent systemic review and meta-analysis add to our current knowledge on vitamin D status as measured by 25-OH vitamin D and IVF outcomes. In the January 2018 edition of Human Reproduction, eleven previously published studies were analyzed. This review found a high prevalence of vitamin D deficiency with only 25.7% of patients having vitamin D levels above 30 ng/ml. The authors concluded that women who were replete (25-OH vitamin D > 30ng/ml) in vitamin D were more likely to achieve a positive pregnancy test, clinical pregnancy and live birth with IVF. There is no association observed between vitamin D status and miscarriage.
Past studies have shown mixed results. It has been proposed that vitamin D is important for the embryo to be able to successfully implant and develop within the uterus.

Unfortunately, there are no prospective studies demonstrating that Vitamin D supplementation in women or men with insufficient or deficient levels of 25-OH Vitamin D will result in an increase in the live birth rate. Such studies are still needed. Adequate Vitamin D levels during pregnancy may help prevent complications such as fetal growth restriction, preterm labor, pregnancy-related hypertension (pre-eclampsia) and gestational diabetes.

Conclusions

1. I advise that all women attempting pregnancy to have their 25-OH vitamin D level tested.
2. We have yet to determine the ideal level of 25-OH vitamin D for fertility. At this time, 25-OH vitamin D levels above 30 ng/mL appear to be most beneficial.
3. Supplementing vitamin D before pregnancy, if needed, will allow for optimal vitamin D levels during pregnancy.
4. The safe upper limit of 25-OH vitamin D is likely 60 ng/ml. Too much vitamin D can be potentially toxic!
5. Vitamin D supplementation is simple, safe and inexpensive when taken in standard doses.
6. In those women who are found to be either vitamin D insufficient or deficient, Vitamin D supplementation should be utilized. Typical supplementation doses are 2000-4000 IU daily of vitamin D3 daily. For vegans, consider vitamin D3 from lichen and or a vitamin D2 product.
7. Vitamin D repletion (reaching an adequate level of vitamin D) may take 60-90 days. Be patient.
8. To enhance the absorption of vitamin D, take your vitamin D supplement with a fat-containing meal.

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