Vitamin D During Pregnancy: Why it Matters

Vitamin D During Pregnancy: Why it Matters

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The sunshine vitamin, otherwise known as Vitamin D is well known for its role in bone development, immune function, and mood. However, more recently the role and benefits of Vitamin D during pregnancy has increasingly become of interest. 

Here we will dive into:

  • The importance of Vitamin D for both you and your baby
  • Risks of Vitamin D deficiency during pregnancy
  • Sources of Vitamin D 
  • Vitamin D in prenatal supplements

Before we dive into Vitamin D and pregnancy, let’s first discuss what Vitamin D is!

What is Vitamin D?

Vitamin D is known as a fat soluble vitamin. However, it is interesting because unlike other vitamins it is also considered a hormone given its role in calcium regulation in our blood and bones. 

Vitamin D also plays an important role in:

Now that we know Vitamin D plays an integral role in many bodily functions, you might be wondering: why is Vitamin D important during pregnancy?

Benefits of Vitamin D and Pregnancy

As previously mentioned, Vitamin D is well known for its role in skeletal, cardiovascular, immune, and muscular function; all of which are important functions necessary for a healthy pregnancy. 

Importance of Vitamin D for Mom

Recent research has shown that pregnant women who took higher doses of Vitamin D to maintain a sufficient level had a lower risk of pregnancy complications such as:

Vitamin D is also involved in many regular bodily functions that aid in a healthy pregnancy including:

  • Aiding in implantation
  • Regulating hormone levels
  • Regulating blood sugar and insulin levels
  • Supporting overall growth and development of baby
  • Promoting proper development of baby’s lungs

Given the many roles Vitamin D takes part in during pregnancy, it is important to have adequate levels of Vitamin D as early as the first trimester, and even while trying to conceive. 

Importance of Vitamin D for Baby

In addition to the health implications of mom, it is also known that a mother’s Vitamin D level directly impacts baby’s level and overall health as well.

From the very beginning, Vitamin D helps your baby in the womb to absorb minerals such as calcium and phosphorus. This helps your baby grow and develop strong bones. Infants born with vitamin D deficiency are more likely to have rickets or soft bones. 

Other research suggests that pregnant women who have sufficient doses of Vitamin D have healthier newborns with decreased risk of immune system disorders. 

Vitamin D and Pregnancy: Why it Matters and How to Get More of It; Importance of Vitamin D During Pregnancy; Spend More Time In the Sun; Eat Food Sources of Vitamin D; Take a Prenatal Vitamin With an Adequate Dose of Vitamin D

Vitamin D Deficiency During Pregnancy

Unfortunately, Vitamin D deficiency is very common during pregnancy.

Anywhere from 40 to 60% of the population is Vitamin D deficient. This includes pregnant women, affecting up to 86% of pregnant women in some countries. 

Vitamin D deficiency correlates with a variety of complications for the mother during pregnancy including preeclampsia and preterm birth

Another issue that pregnant women can encounter from Vitamin D deficiency is gestational diabetes. Emerging evidence suggests that Vitamin D administration can improve insulin sensitivity and glucose tolerance.

Lastly, Vitamin D deficiency in pregnant women has been shown to result in newborns with asthma and some autoimmune disorders. 

How Do I Know if I am Vitamin D Deficient?

Given the high rates of Vitamin D deficiency during pregnancy and the health implications associated with Vitamin D deficiency, you would think it would be a standard test to screen for during pregnancy. However, unfortunately this is not the case. 

Although it is not a standard test during pregnancy, screening for Vitamin D deficiency can be done with a simple blood test for the circulating levels of 25-hydroxy Vitamin D (the storage form of vitamin D). What is considered an adequate level of Vitamin D varies from institution to institution. However, most can agree that optimal levels typically range anywhere from >30 – 50 ng/ml.

Discuss with your provider if screening for Vitamin D deficiency is right for you. Then, continue to read on to learn how you can get more Vitamin D through sun, food, and supplements, and what the recommended supplemental doses are. 

How Much Vitamin D Do I Need During Pregnancy?

While the Institute of Medicine (IOM) suggests 600 IU of vitamin D intake for pregnant women, this guideline is still under debate. 

A recent randomized controlled trial conducted on Vitamin D supplementation in pregnant women has shown that up to 4,000 IU taken per day is not only safe, but optimal during pregnancy to sustain sufficient levels.  

Additionally, if you are currently Vitamin D deficient during pregnancy, you may need higher supplemental doses to reach adequate levels before receiving a maintenance dose.

Please note, too much of a good thing is not always a good thing. Although rare, Vitamin D toxicity is possible when supplemented in large doses (we’re talking upwards of 60,000 IU daily for an extended period of time).

Again, work with your healthcare provider about screening for Vitamin D deficiency and what the recommended dose for repletion and maintenance for you may be. 

How to Get More Vitamin D

Vitamin D from the Sun

Humans only get a small portion of their Vitamin D intake from food. Our bodies make most of our Vitamin D from sun exposure (up to 90%). 

Many factors influence the body’s ability to absorb and produce vitamin D including:

Location and season

Where you live geographically and the season you are in can impact the amount of daylight and thus sun exposure. If you live somewhere where there is limited daylight, and during winter and spring time you are at increased risk of Vitamin D deficiency.

Amount of time you spend outside without sunscreen

Sunscreen acts as a barrier to the rays of sunlight, thus limiting your exposure and decreasing the amount of Vitamin D your skin synthesizes. Spending even 5 – 10 minutes outside without sunscreen a few times a week can increase your Vitamin D levels.

Age 

As you age your ability to synthesize Vitamin D decreases, thus you are at an increased risk of deficiency. 

Weight or Body Mass Index (BMI)

Low Vitamin D levels have been found with higher BMI status (>30 kg/m2). The higher your BMI, the more at risk you are for a Vitamin D deficiency.

Skin pigmentation

Melanin, a natural pigment in our skin, acts as a natural barrier to the sun’s rays. People with darker colored skin are at a higher risk for Vitamin D deficiency and may require more exposure to sunlight and/or supplementation.

Vitamin D from Food

As just discussed, while the majority of our Vitamin D comes from sun exposure, it doesn’t hurt to incorporate Vitamin D rich foods in our diet too. 

Many of us think that Vitamin D in food comes from dairy alone. However, fortified non-dairy milk, other fortified foods and beverages, and eggs are also sources of vitamin D.

Food Sources of Vitamin D

Food Sources of Vitamin D

  • Egg yolks
  • Mushrooms
  • Cod liver oil, salmon, mackerel, sardines (fatty fish)
  • Fortified:
    • Cereals
    • Milk
    • Plant-based milks
    • Orange juice

Vitamin D Supplementation and Pregnancy

While I typically recommend a foods first approach, even the food sources of Vitamin D listed above supply only small amounts of Vitamin D. Therefore, if you are not receiving adequate sunlight exposure (such as during the winter time), or have a baseline Vitamin D deficiency prior to, or during pregnancy, a Vitamin D supplement is typically recommended to achieve optimal levels.

Vitamin D2 (Ergocalciferol) vs Vitamin D3 (Cholecalciferol)

Before we dive into Vitamin D supplementation doses, I would like to note that there are two forms of vitamin D: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol).

Vitamin D2, ergocalciferol, is found primarily in plant-based sources and fortified products. Cholecalciferol (Vitamin D3) is derived from animal sources such as fish livers. When our bodies are exposed to the sun, our skin produces vitamin D3 . 

Cholecalciferol (Vitamin D3) is the preferred form of supplementation as some studies have shown it to be more effective in raising Vitamin D levels in the body. 

Vitamin D in Prenatal Supplements

*Please note, this section of the article  includes affiliate links.

There is a lot of controversy surrounding the importance of Vitamin D in prenatal supplements. 

As previously mentioned, supplementation of up to 4,000 IU of Vitamin D in pregnant women has not only been shown to be safe, but may be the optimal dose during pregnancy to sustain sufficient levels.  

Most prenatal vitamins contain 1/10 of the recommended daily dose of Vitamin D stated above, or 400 – 600 IU. However, a few prenatal vitamins on the market have taken into consideration this emerging evidence and have included 4,000 IU of Vitamin D in their formulation. 

These include:

Whether you take a prenatal vitamin with a higher dose of Vitamin D, or add an additional Vitamin D supplement to your prenatal vitamin, work with your healthcare provider or registered dietitian to screen your levels and to determine the right amount of supplementation for you. 

In Summary

Women who lack Vitamin D during pregnancy are more likely to have complications during pregnancy. 

While newer research suggests that up to 4,000 IU of Vitamin D during pregnancy can be sufficient, the only way to know the optimal dose for you is to know your circulating storage levels of 25-hydroxy Vitamin D.

In the meantime:

  • Get sun exposure from time to time: 5-10 minutes of sun exposure is healthy a few times per week 
  • Eat more food sources of Vitamin D
  • Take your prenatal vitamin

“Vitamin D During Pregnancy: Why it Matters” is written by Emilia Snyder. Edited/reviewed by Jamie Adams, MS, RD, LDN. Emilia is a chemical engineer, nature lover, and women’s health enthusiast who enjoys communicating scientific ideas to the general public.

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