Vitamin D, fertility, and pregnancy

Vitamin D is an important vitamin that regulates calcium levels in the blood and helps maintain balance in the body's immune system. Vitamin D is absorbed by the body from sunlight and can also come from fatty fish, eggs, and cheese. Today, the Danish Health Authority recommends that all pregnant women take a daily supplement of 10 micrograms throughout pregnancy, but several research studies have also shown that vitamin D may have an impact on women's fertility.

Vitamin D and Fertility

Several studies have examined the link between vitamin D and female fertility. Among other findings, researchers have discovered that women with low levels of vitamin D have more difficulty getting pregnant and face a higher risk of miscarriage.

In this 2019 study, 500 women diagnosed with infertility (infertility is defined as trying to conceive for more than a year without success) were examined. The study found that 84% of these women had a vitamin D deficiency.

The reason is likely that vitamin D plays a role in the uterine lining’s ability to receive a fertilized egg, which must successfully implant in the uterus to result in pregnancy. We also know that vitamin D influences the balance of the immune system, and a suppressed immune response may negatively affect a woman's fertility.

Read more about fertility and try our fertility calculator here

Vitamin D and Male Fertility
In men, low levels of vitamin D can also negatively affect fertility.

A study conducted at Rigshospitalet examined 330 infertile men who were known to have a vitamin D deficiency. The men were given either a placebo or vitamin D supplements. The study showed that the men who received vitamin D doubled their chances of spontaneous conception compared to the group who received the placebo (a placebo is a treatment with no medical effect).

However, the study also found that vitamin D does not increase sperm production in men with only slightly reduced vitamin D levels. So not all men will experience improved fertility from taking daily vitamin D supplements.

Keep in mind that it takes about three months from when a sperm cell is formed until it is ready to fertilize an egg. Therefore, men need to take supplements for three months before it can have a real impact on their sperm quality.

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Find our supplements for female fertility here

How Much Vitamin D Should You Take?
Today, many Danish fertility clinics recommend that women have their vitamin D levels checked before starting fertility treatment. If the level is low (below 50 nmol), a daily supplement of 20 micrograms of vitamin D is advised.

Vitamin D for Pregnant Women
The Danish Health Authority currently recommends a daily supplement of 10 micrograms of vitamin D throughout pregnancy. This is because the body needs vitamin D to absorb calcium and process it correctly.

We know that vitamin D is essential for the baby’s growth and bone development. If the mother is deficient in vitamin D during pregnancy, the baby will also be born with too low a level of vitamin D.

Vitamin D and Miscarriage
A 2015 research study from the University of Southern Denmark found that women with a vitamin D deficiency have twice the risk of miscarriage in early pregnancy (before week 12). The study was based on 1,683 women who had their vitamin D levels measured in early pregnancy. Of those, 59 experienced a miscarriage.

Vitamin D and Breastfeeding
The Danish Health Authority recommends that breastfeeding women take a daily supplement of 10 micrograms of vitamin D while they are nursing.

Vitamin D for Babies and Children
All children are recommended to receive a daily supplement of 10 micrograms of vitamin D from the age of 2 weeks until they turn 4 years old.

Vitamin D is usually given to babies in drop form until they are old enough to chew a vitamin tablet (typically between 1.5 and 2 years old).

Vitamin D for Children with Dark Skin
If the child has darker skin or is often covered by long sleeves, trousers, dresses, or scarves, it is recommended that they receive 10 micrograms of vitamin D daily throughout childhood.

Vitamin D and Infant Formula
If your infant consumes more than 800 ml of formula per day, with at least 1.3 micrograms of vitamin D per 100 ml, then an additional vitamin D supplement is not necessary.

The Danish Health Authority has created a chart that shows when an extra vitamin D supplement in drop form is needed, based on the daily amount of formula and its vitamin D content.