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Is Vitamin D Safe for Fertility, Pregnancy & Breastfeeding?

Written by Ana Aleksic, MSc (Pharmacy) | Last updated:
Evguenia Alechine
Puya Yazdi
Medically reviewed by
Evguenia Alechine, PhD (Biochemistry), Puya Yazdi, MD | Written by Ana Aleksic, MSc (Pharmacy) | Last updated:

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Vitamin D Safety During Pregnancy and Breastfeeding

If you’re pregnant or trying to conceive, nothing is more important than making sure you get the nutrients you need while avoiding any potentially harmful compounds. But what about vitamin D? Is the “sunshine vitamin” safe? Can it improve fertility and support a healthy pregnancy? And should you worry about getting enough if you’re breastfeeding? Read on to get evidence-based answers to all these questions and more.

Vitamin D Status & Reproductive Health

Vitamin D or the “sunshine vitamin” is an essential fat-soluble vitamin.

The body naturally makes vitamin D when exposed to sunlight. Getting regular, moderate sun exposure is a safe way to maintain normal vitamin D levels during the summer months.

Vitamin D is also found in certain foods, such as fatty fish like salmon and sardines. Additionally, many vitamin D supplements are available on the market.

The recommended daily intake of vitamin D for children above 1 year old and adults up to 70 years old is 600 IU. The recommended intake stays the same for pregnant and breastfeeding women. Newborns and babies require at last 400 IU/day until 12 months [1].

Remember to talk to your doctor before supplementing, especially if you are pregnant, breastfeeding, or trying to conceive!

Vitamin D is an essential vitamin made in the skin during sunlight exposure and found in some foods. Adults under 70 years old and breastfeeding and pregnant women should aim to get 600 IU/day.

Vitamin D in Pregnancy

Snapshot

  • Required at 600 IU/day for general health
  • Women with dark skin or wearing concealing clothes are at a greater risk of deficiency
  • Some doctors may screen pregnant women at risk of deficiency
  • Deficiency during pregnancy may impair bone health in both the mother and baby
  • Most experts consider doses up to 4000 IU/day safe in vitamin D-deficient pregnancies

Who is at Risk of Deficiency?

According to some estimates, vitamin D deficiency was high in a diverse group of women during pregnancy, affecting 97% of African Americans, 81% of Hispanics, and 67% of Caucasians. Mothers with dark skin or wearing concealing clothes are at great risk of vitamin D deficiency [2, 3, 4].

Health Effects of Deficiency

Deficiency during pregnancy may affect both the mother and the baby.

Studies propose deficiency could lead to bone loss and osteomalacia in the mother. In newborns, it may cause impaired growth, bone, and enamel formation. Limited evidence suggests deficiency may also increase the risk of type 1 diabetes, asthma, and schizophrenia in newborns, though solid data are lacking to back up these findings [5, 6, 7, 8, 9].

A couple of studies have linked vitamin D deficiency during pregnancy with:

  • An increased risk of preeclampsia, the leading cause of maternal and neonatal morbidity and mortality [10, 11].
  • Almost 4 times the odds of primary cesarean section [12].
  • Bacterial vaginosis, a highly prevalent vaginal infection that is associated with adverse pregnancy outcomes [13].

These findings are inconclusive. Additional studies with larger samples are needed to replicate them.

Additionally, some scientists think vitamin D sufficiency may protect from spontaneous preterm birth risk. More research is needed [14].

Safety & Potential Benefits of Supplementation

When doctors identify vitamin D deficiency during pregnancy, most agree that 1,000–2,000 IU per day of vitamin D is safe. Data on the safety of higher doses are lacking. Nonetheless, most experts at the American College of Obstetricians and Gynecologists consider doses up to 4000 IU/day safe in pregnant and breastfeeding women [15].

However, taking doses above 4000 IU/day can be harmful. Vitamin D supplements may also interact with prescription medications.

However, experts concluded that ongoing randomized clinical trials need to be completed to determine if vitamin D supplements (beyond that contained in prenatal vitamins) should be routinely recommended to pregnant women. Currently, evidence is lacking to recommend vitamin D supplementation for the prevention of preterm birth or preeclampsia [15].

Most experts consider vitamin D doses up to 4000 ID/day safe during pregnancy. Evidence is lacking to suggest supplementation can prevent preterm birth and preeclampsia, though.

Vitamin D & Breastfeeding

It was thought for decades that breast milk was naturally low in vitamin D.

Since vitamin D is transferred into the milk, the mother needs a daily source of vitamin D in order to provide her infant with enough substrate to avoid deficiency [16].

According to the latest recommendations, breastfeeding women need just 600 IU/day [1].

One study posited that breastfeeding women need to take in 6000 IU/day of vitamin D to provide their baby with the required amount of vitamin D (400 IU/day). Larger studies have yet to confirm this hypothesis [17].

Women who are not breastfeeding can provide their babies with vitamin D using a fortified formula [17].

Babies need 400 IU/day of vitamin D. Breastfeeding women should aim to get 600 IU/day. Data are lacking to support the benefits of higher doses.

Vitamin D & Fertility

Snapshot

  • Supports reproductive health
  • Limited evidence suggests vitamin D may improve fertility in men
  • Small studies point at the potential of vitamin D to improve PCOS symptoms

May Improve Fertility in Men

Studies on mice show beneficial effects of vitamin D on the male reproductive system [18].

Male mice who lack vitamin D receptors suffer from infertility. Deficient mice had decreased sperm count and motility and structural abnormality of the testes [19, 20, 21, 22].

Scientists think that vitamin D is important for sperm production, growth, and survival [23].

The vitamin D receptor and the vitamin D metabolizing enzyme are present in the male reproductive tract including the testes, sperm, ejaculatory tract, and prostate [24, 25, 26, 27].

Limited studies have associated higher vitamin D blood levels with better sperm motility, which is an important fertility facto [28, 29].

In one study, men with vitamin D deficiency (blood levels <20 ng/mL) had less motile sperm compared with men with high levels. However, blood levels above 50 ng/mL were associated with decreased sperm production and quality. The researchers concluded that 20-50 ng/mL of vitamin D is the ideal range for the proper functioning of the male reproductive system. Their findings have not yet been replicated [28, 29].

Vitamin D might support men’s reproductive health and fertility. Limited studies suggest vitamin D may improve sperm motility.

Fertility Effects in Women?

Data on the effects of vitamin D on fertility in women is sparse. Limited evidence suggests it may help women with PCOS, which impacts ovulation and fertility. Large-scale, clinical studies are needed.

Women with polycystic ovary syndrome (PCOS) tend to have low vitamin D blood levels. Vitamin D supplementation might improve sugar balance and menstrual frequency in PCOS women (30, 31, 32, 33, 34).

What’s more, women with PCOS are at an increased risk of cardiovascular disease. Limited research suggests that low-dose vitamin D may help as an add-on for women who suffer from both PCOS and cardiovascular disease [35].

Women with PCOS often have fertility problems. Small-scale studies suggest low-dose vitamin D might improve menstrual frequency in women with PCOS.

Takeaway

Vitamin D supports fertility reproductive health. Pregnant women should get 600 IU of vitamin D per day, which equals the amount they needed to get before becoming pregnant to avoid deficiency. Babies up to 12 months need 400 IU/day, which breastfeeding mothers with normal vitamin D intake can provide. Fortified formulas are an option for women who are not breastfeeding. However, solid evidence is lacking to support vitamin D doses above those found in prenatal vitamins whether you are trying to conceive, are pregnant, or breastfeeding. Limited evidence suggests vitamin D may improve PCOS in women. Promising findings from animal studies reveal vitamin may play a role in sperm motility. These findings are still inconclusive and additional studies are needed.

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About the Author

Ana Aleksic

Ana Aleksic

MSc (Pharmacy)
Ana received her MS in Pharmacy from the University of Belgrade.
Ana has many years of experience in clinical research and health advising. She loves communicating science and empowering people to achieve their optimal health. Ana spent years working with patients who suffer from various mental health issues and chronic health problems. She is a strong advocate of integrating scientific knowledge and holistic medicine.

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