The Role of B Vitamins During Pregnancy

There are eight B vitamins, collectively referred to as the vitamin B complex, and they are a critical component of prenatal nutrition. In this guide, we’ll discuss all eight B vitamins, including which ones to look for in a prenatal. 

By Dr. Kenosha Gleaton

You have probably heard of biotin (B7), folate (B9), and B12 (cobalamin), but may be less familiar with pyridoxine (B6) and thiamin (B1). All these nutrients are part of the B vitamin family. There are eight B vitamins, collectively referred to as the vitamin B complex, and they are a critical component of prenatal nutrition. In this guide, we’ll discuss all eight B vitamins, including which ones to look for in a prenatal vitamin for women.

What Are B Vitamins?

B vitamins help your body convert food into energy and also help form red blood cells. [1] They are a class of water-soluble vitamins, meaning they are readily absorbed into your body for immediate use. Because they are not stored in the body (like calcium), they need to be replenished regularly via diet and supplements. 

B Vitamin Intake During Pregnancy

Let’s look at all of the B vitamins and their recommended intake [2-9]:

• Vitamin B1 (thiamin)
• The RDA (Recommended Dietary Allowance) for females over 19 is 1.1mg and 1.4 mg during pregnancy.
• Vitamin B2 (riboflavin)
• RDA for females 19+ is 1.1 mg and 1.4 mg during pregnancy.
• Vitamin B3 (niacin)
• RDA for females 19+ is 14 mg and 18 mg during pregnancy.
• Vitamin B5 (panthothenic acid)
• RDA for females 19+ is 5 mg and 6 mg during pregnancy.
• Vitamin B6 (pyridoxine)
• RDA for females 19+ is 1.3 mg and 1.9 mg during pregnancy.
• Vitamin B7 (biotin)
• AI (adequate intake) for females 19+ is 30 mcg (no change for pregnancy).
• Read about the benefits of bioin supplements >> 
• Vitamin B9 (folate)
• RDA for females 19+ is 400 mcg and 600 mcg during pregnancy.
• Learn about the difference between folate and folic acid >> 
• Vitamin B12 (cobalamin)
• RDA is 2.4 mcg for 14+ and 2.6 mcg during pregnancy.

Which B Vitamins Are Important During Pregnancy?

All eight of the B vitamins are recommended for adults, including during pregnancy. The ones you may hear about the most often include:

Folate

Folate plays a critical role in the prevention of neural tube defects (NTDs) in a developing baby. NTDs are deformities of the neural tube, which is the embryonic precursor to the brain and spine. During a healthy pregnancy, the tube will seal itself off between three and four weeks of fetal development. [10] In the case of an NTD, the tube doesn’t fully close, leading to devastating and life-threatening conditions like spina bifida. 

Research has shown that folate supplementation reduces the incidence of NTDs significantly. [11] The results of these studies prompted the United States government to institute a folic acid food fortification program in 1998 so that all women of childbearing age would consume extra folate in their diet. [12] Since the implementation of food fortification, NTDs have decreased in the US by 35%. [13] We don’t yet fully understand how folate supplementation lowers NTD risk, but we know that it involves decreasing levels of homocysteine, an amino acid which is also tied to a higher risk of heart disease and stroke. [14-16] 

 Besides helping to prevent NTDs, folate is also essential for creating new DNA, proteins, and red blood cells, the cells that transport oxygen throughout the body. [8] 

Folate is naturally present in a wide variety of foods, including vegetables (especially dark green leafy vegetables), fruits, fruit juices, nuts, beans, peas, seafood, eggs, dairy products, meat, poultry, and grains. [8] Spinach, liver, asparagus, and brussels sprouts are among the foods with the highest folate levels. Are you getting enough folate? Find out >> 

Vitamin B6

According to the World Health Organization, vitamin B6 is important for several metabolic processes, as well as the development and functioning of the nervous system, primarily through the biosynthesis of neurotransmitters. [17] It has been previously suggested that vitamin B6 might play a role in the prevention of pre-eclampsia and possibly preterm birth. [6] However, current literature reviews indicate that there is insufficient evidence on the benefits and harms of routine vitamin B6 (pyridoxine) supplementation during pregnancy, though it may provide some relief from pregnancy-related nausea.

Vitamin B6 is found in a wide variety of foods including fish, beef liver, other organ meats, potatoes, other starchy vegetables, and fruit (other than citrus). [6] 

Vitamin B12

Vitamin B12 is important for maintaining the health of your nervous system and the brain development and growth of a fetus. [9,18] Studies show that vitamin B12 deficiency is associated with adverse maternal and neonatal outcomes, including developmental anomalies, miscarriage, preeclampsia, and low birth weight. [18] 

Vitamin B12 is naturally found in animal products, including fish, meat, poultry, eggs, milk, and milk products. [12] The Academy of Nutrition and Dietetics recommends supplemental vitamin B12 for vegans and lacto-ovo vegetarians during both pregnancy and lactation to ensure that enough vitamin B12 is transferred to the fetus and infant. [19] 

Natalist Hydration & Energy Electrolyte Drink Mix includes B12 and other vital nutrients to support energy levels and hydration!

Can You Have Too Much Vitamin B?

Any supplement routine, especially while pregnant, should be reviewed with your doctor. If you take a prenatal gummy and an additional supplement, you may be getting too much of one nutrient.

Some vitamins have Tolerable Upper Intake Levels (ULs), which is the maximum amount of a vitamin you can take daily without increasing your risk for negative health effects. ULs have been established for Vitamins B3, B6, and B9. However, the rest are not determined because there is insufficient scientific evidence from which to set these levels, or there’s a low potential for toxicity. 

Tolerable upper intake levels (ULs) for B vitamins during pregnancy set by the Institute of Medicine for the United States and Canada include [20]:

• B1 (thiamin): not determined
• B2 (riboflavin): not determined
• B3 (niacin): 35 mg/day
• B5 (pantothenic acid): not determined
• B6 (pyridoxine): 100 mg/day
• B7 (biotin): not determined
• B9 (folate): 1000 ug/day
• B12 (cobalamin): not determined

Should I Take Vitamin B Complex When Trying to Conceive?

Yes, B vitamins should be in your prenatal, which should be taken while you are trying to conceive. Make sure your prenatal contains at least 600 mcg of folate (not folic acid), and the recommended intake levels described in the above section. [8,20] 

Key Takeaways

• There are eight B vitamins that are referred to as “vitamin B complex.”
• B vitamins are water-soluble, meaning they are readily absorbed into your body for immediate use and need to be replenished regularly via diet and supplements.
• B vitamins are especially important while trying to conceive and pregnant.
• Make sure your prenatal vitamin contains the recommended amount of B vitamins, especially folate, B6, and B12.

Originally published 01/04/2021. Updated for accuracy and relevancy on 01/19/2024. 

Dr. Kenosha Gleaton is board-certified in gynecology and obstetrics and is the Medical Advisor of Natalist. She received her MD from MUSC and completed her residency at Carolinas Medical Center in Charlotte, NC.

Dr. Gleaton is passionate about women, health equity, and mentoring. She is the CEO of The EpiCentre, an OBGYN spa-like practice, and is a Clinical faculty member of Charleston Southern University. She is also a member of the American College of Obstetrics & Gynecology, the American Association of Gynecologic Laparoscopists, and the American Association of Professional Women