The Importance of Vitamin D in Pregnancy and Fertility

Vitamin D, our sunshine vitamin, has traditionally been recognized in supporting bone health. In more recent years, our appreciation for Vitamin D has evolved, and we now know that vitamin D does so much more than keep our bones strong. Its benefits have been studied with respect to cancer prevention, immune support, mood disorders, hypertension, diabetes and autoimmune conditions. Now there is emerging evidence that Vitamin D is important to add to the pre-pregnancy supplement routine to support fertility and healthy pregnancy.

Recently we’ve found that there are Vitamin D receptors and enzymes that use Vitamin D in reproductive tissues. This has lead to the following new and exciting fertility research:

•       Women with adequate Vitamin D levels have higher pregnancy rates when undergoing IVF (52.5% vs 37.4% in a study of 173 women in Toronto)   Adequate Vitamin D was associated with fewer uterine fibroids

•       High doses of vitamin D lower estradiol. Estrogen dominance is one of the main causes of infertility and a host of other problems

•       Vitamin D may have a direct effect on AMH, thus leading to a better ovarian reserve in women with optimal Vitamin D levels

•       Vitamin D has been shown to help women with PCOS ovulate more regularly, increase endometrial/uterine thickness, improve insulin sensitivity, lower cholesterol and normalize AMH

Several new studies have also indicated that low Vitamin D levels in early pregnancy are associated with a higher risk of developing gestational diabetes mellitus, which puts mom and baby at greater risk of developing type 2 diabetes. Since Vitamin D helps to improve insulin sensitivity and glucose tolerance, some believe that supplementing Vitamin D pre-pregnancy should be just as important as folic acid supplementation.

So how do we get enough Vitamin D?

Vitamin D is a fat soluble vitamin.  It is found in mushrooms, certain fatty fish, eggs, milk and many milk alternatives.  Our main source of Vitamin D is sunlight – the body can make Vitamin D from cholesterol when our skin is exposed to adequate amounts of sun.  Unfortunately, most of us don’t get enough sunshine, especially in the winter months, and in the summer months sunscreen blocks out the UV rays that our body needs to make Vitamin D.

While Vitamin D has received widespread attention, checking your levels is largely a “user-pay” test.  Public health care in Ontario will only cover Vitamin D testing for patients with the following medical conditions: rickets, osteoporosis/osteopenia, renal disease, malabsorption syndromes and patients on medications that affect vitamin D metabolism. Serum 25- Hydroxy Vitamin D should be measured to assess nutritional vitamin D status and to diagnose vitamin D deficiency and to check the effect of treatment. As with most supplements, it is important to speak to your healthcare provider regarding testing and appropriate vitamin D dosing for your specific needs.