Does vitamin D influence pregnancy and fertility?

Vitamin D is commonly known to be related to bone and calcium metabolism. However, the presence of receptors for this vitamin in the ovary, uterus, and placenta has put it in the spotlight in relation to fertility and pregnancy.

Vitamin D deficiency in women of reproductive age is quite common. Serum vitamin D levels above 30 ng/ml are considered sufficient according to reference values. If vitamin D levels are between 21 and 29 ng/ml we speak of insufficiency, and if they are less than 20 ng/ml it is a deficiency.

Vitamin D and fertility

There are numerous studies linking vitamin D levels and reproductive capacity in women and men.

The effect of vitamin D on female and male fertility is detailed below.

Female fertility

According to several scientific studies, vitamin D improves the conditions for embryo implantation, due to its action on the endometrium. This is thanks to the anti-inflammatory and immunomodulatory effect of vitamin D on the immune system, as it is necessary for the embryo to be immunologically tolerated by the mother. In addition, this vitamin would produce the activation of genes related to implantation.

Similarly, an increase in progesterone secretion by ovarian granulosa cells has also been described. This hormone is essential for the pregnancy to evolve and be maintained.

Effects of vitamin D on female fertility

However, vitamin D has been related to anti-mullerian hormone (AMH), a good marker of ovarian reserve, that is, the number of eggs a woman has at a given time.

In addition, vitamin D deficiency would affect endometriosis, polycystic ovarian syndrome (PCOS), uterine fibroids and increase miscarriages. All this causes difficulty in achieving a pregnancy and that this is evolutionary. Therefore, if vitamin D levels are adequate, a woman will have less risk of suffering from some of these gynecological conditions or will improve them and, therefore, will have a better prognosis at the time of seeking pregnancy.

However, more studies are still needed to provide a more conclusive result on the involvement of vitamin D in all these aspects of female fertility and pregnancy.

Male fertility

Vitamin D has been associated with sperm production (spermatogenesis) and maturation.

Adequate vitamin D levels appear to improve sperm motility in the seminogram. Another effect of vitamin D supplementation in males is that it may increase levels of testosterone, the male sex hormone produced by the testes.

Vitamin D effects on male fertility

However, as in the case of women, more conclusive studies are needed to corroborate the benefit of this vitamin on male fertility.

Vitamin D in pregnancy

Another relationship of vitamin D that has been studied has been with pregnancy. Vitamin D deficiency in pregnant women may lead to an increased risk of obstetric complications. Some of the problems a pregnant woman with low vitamin D levels may have are as follows:

• Preeclampsia.
• Delayed fetal growth.
• Gestational diabetes.
• Increased risk of cesarean section.
• Postpartum depression.

Obstetric problems with vitamin D deficiency in pregnancy

In addition, a vitamin D deficiency in pregnant women would also generate a higher probability of suffering a miscarriage.

In the event of a lack of vitamin D, the specialist may advise supplementation. It is important that it is done under medical control with a dosage adjusted by the specialist.

Sources of vitamin D

Our body produces around 80-90% of vitamin D thanks to the effect of solar radiation on the skin. Therefore, the most advisable is a moderate daily exposure to the sun of about 15 minutes (avoiding the central hours of the day, which would be harmful to the skin) to maintain adequate levels of vitamin D.

However, the remaining 10-20% of vitamin D is acquired through the diet by eating certain foods rich in this vitamin, such as, for example:

• Oily fish such as salmon.
• Egg Yolk.
• Liver.
• Milk, cheese and yogurts, especially if fortified.
• Mushroom.

Foods rich in vitamin D

When a person has low vitamin D levels, vitamin D supplementation is possible.

Women who are seeking to become pregnant, either naturally or through assisted reproduction treatment, can consult a specialist to find out their vitamin D levels.

In the event that these amounts are lower than recommended, the specialist will prescribe vitamin supplements and adjust the dose to maintain adequate levels.

FAQs from users

What are the consequences of low vitamin D levels in pregnancy?

Vitamin D levels are of vital importance during pregnancy, as vitamin D deficiency can lead to an increased risk of preeclampsia, gestational diabetes, impaired immune system and low birth weight of the newborn.

Vitamin D has multiple and vital physiological functions such as regulation of metabolism, maintenance of bones and teeth, involvement in the proper functioning of the immune system and participation in the process of insulin secretion.

According to a Cochrane review, supplementation of pregnant women with vitamin D alone is likely to reduce the risk of pre-eclampsia, gestational diabetes and low birth weight, and may reduce the risk of severe postpartum hemorrhage. It is not well known whether it may influence the risk of preterm delivery at less than 37 weeks' gestation.

¿Afecta la vitamina D a la implantación embrionaria?

Although traditionally importance has been given only to the role of vitamin D in bone health, its possible role in fertility is gaining increasing interest. This vitamin has receptors throughout the body, including the ovary, endometrium and placenta, and has been linked to reproductive and obstetric outcomes.

Optimal vitamin D levels have been shown in several studies to improve the likelihood of pregnancy. However, the mechanism by which it increases the rate of gestation is still not very clear.

In a study carried out in recipients of donor eggs, in which it is assumed that all the embryos will be of good quality, it was observed that those patients with correct vitamin D levels had a greater chance of becoming pregnant. However, in another study performed with euploid embryo transfer (chromosomally healthy), this effect was not observed. Thus, although the evidence seems to indicate that vitamin D does improve endometrial receptivity, its role is probably more complex than it appears at first glance.

Another possible mechanism by which vitamin D could increase pregnancy rates is by improving oocyte quality. It has been shown that blood levels of vitamin D are proportional to follicular fluid levels, and it is thought that vitamin D may alleviate ovarian aging, although it has not been studied directly in oocytes.

Does vitamin D influence IVF treatments?

It has been shown that women with adequate vitamin D levels have a higher probability of success after IVF treatment than women with a deficiency. However, other studies have not observed this relationship, so more studies are needed to support or rule out the usefulness of vitamin D supplementation in assisted reproduction treatment patients with a deficiency.

Do I need vitamin D supplements during pregnancy?

The decision whether or not to administer vitamin D during pregnancy will be made by the physician based on the woman's vitamin D levels.

A systematic review found that vitamin D could reduce the risk of low birth weight and preterm delivery, while if given together with calcium it would reduce the risk of preeclampsia. However, the latter combination would increase the risk of preterm delivery.

Despite this, it was concluded that there is not enough evidence to give vitamin D supplements to all pregnant women in order to improve obstetric and neonatal complications.

Does vitamin D level matter for egg preservation?

In summary, while vitamin D may play a role in egg preservation and fertility in general, it is essential to understand that this relationship is complex and that there is no one-size-fits-all solution. Consultation with a fertility specialist and individualized assessment are critical to address each woman's reproductive health needs.
Read more

What is the relationship between systemic lupus erythematosus and vitamin D?

Vitamin D deficiency is more common in people affected by this pathology than in healthy individuals. A lower sun exposure due to the photosensitivity of these patients, and an inability to produce active vitamin D due to renal dysfunction, could explain these findings.

Regarding vitamin D supplementation in these patients, for its immunomodulatory effect, there are contradictory results. While some studies have found no clear relationship in disease activity and serology with vitamin D supplementation, other studies have described a reduction in disease activity due to an immunosuppressive and anti-inflammatory effect.

Recommended readings

If you are interested in fertility and nutrition, we recommend you visit this article: What are the types of foods that promote female fertility?

On the other hand, we have mentioned that vitamin D levels can improve sperm motility. For more information on this topic, you can visit this article: What are normal values in sperm motility analysis?