Vitamin B12 and Pregnancy

Compared to other people, pregnant women have an increased need for vitamin B12. Pregnancy problems could occur with severe vitamin B12 deficiencies, so it is important to treat a deficiency as soon as possible. If you are already taking this vitamin and pregnancy occurs, to your healthcare provider to discuss your need for additional doses of vitamin B12.

Do Pregnant Women Need Vitamin B12 Supplements?

Pregnant women have a slightly increased need for vitamin B12, compared to other individuals. While mild deficiencies are common during pregnancy and are probably no cause for concern, a severe vitamin B12 deficiency can have serious consequences for both a pregnant woman and her developing child.

Am I Getting Enough Vitamin B12 During Pregnancy?

The RDA (Recommended Dietary Allowance) of vitamin B12 for pregnant women is 2.6 mcg per day, compared to 2.4 mcg per day for most other adults. Many women easily get plenty of vitamin B12 through a healthy and well-rounded diet. However, strict vegetarians have a much higher risk for vitamin B12 deficiency. To compound the problem, most women take folic acid during pregnancy. While folic acid is important for preventing birth defects, it can also "mask" some of the signs of a vitamin B12 deficiency, making a deficiency much more difficult to detect.

Vitamin B12 Deficiency During Pregnancy

Vitamin B12 is stored in large quantities in the body. The developing fetus uses up some of the pregnant woman's store of this vitamin, both in the process of development and to build up its own stores. At birth, the baby will have a much higher level of vitamin B12 in the blood than the mother. For most women, this does not appear to be a problem, and mild causes of vitamin B12 deficiency do not seem to increase the risk of birth defects or other problems. In addition, prenatal vitamins contain vitamin B12, almost always in doses significantly higher than the RDA. These higher doses are safe for women, as this vitamin has a low risk of toxicity.
On the other hand, a severe vitamin B12 deficiency can have disastrous consequences. There is evidence that it may cause severe birth defects (including neural tube defects, much like a folic acid deficiency can cause). There is also some preliminary evidence that it may increase the risk of infertility, recurrent spontaneous abortions (miscarriages), and preterm birth. Women with severe vitamin B12 deficiencies will need much more vitamin B12 than in a typical prenatal vitamin. They may even need vitamin B12 injections, at least for awhile.

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Last reviewed by: Kristi Monson, PharmD
Pregnancy and Pain