Not enough vitamin B12 may be to blame for an increased risk of preterm birth, according to new research.

pregnant woman eating salad
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I have been a vegetarian, bordering on vegan, for most of my life. I did not eat meat during any of my three pregnancies, and I stayed away from dairy, so I was especially interested in a new study out of the Norwegian University of Science and Technology, and published in the American Journal of Epidemiology, finding that women who adhere to a vegan diet during pregnancy are more likely to suffer preterm birth.

The reason? It has to do with the potential for vitamin B12 deficiency when not enough meat, eggs, or dairy are consumed. A vegan diet doesn't include any animal proteins or byproducts, which are the sole natural sources of the vitamin. Vitamin B12 is vitally important for healthy brain and nervous system development and functioning.

Researchers looked at 11,216 pregnant women from 11 countries to determine a link between a deficiency of the vitamin and a 21 percent increased risk of preterm birth. The association was present despite the differences in the countries' income levels.

Tormod Rogne, a medical doctor and intern at Akershus University Hospital near Oslo, said, "Low levels of vitamin B12 in pregnant women did not appear to affect the newborn's birth weight." He cautioned that a vegan diet may not be wholly responsible for an increased risk of preterm birth, adding, "Low blood concentrations of vitamin B12 may be related to other factors, such as malnutrition and poverty, which can also affect birth weight and length of pregnancy."

Still, the importance of getting enough B12 during pregnancy is undisputed. Researchers stopped short of recommending that pregnant women take a supplement, saying in a press release, "Although we found that vitamin B12 deficiency is associated with an increased risk of preterm birth, we know very little about the effects of taking vitamin B12 supplements during pregnancy."

We talked to Christine Greves, MD, OB/GYN with Winnie Palmer Hospital for Women & Babies in Orlando to find out what pregnant women who eat a vegan diet can do. "I strongly recommend that she inform her doctor [of her diet] so the appropriate lab testing can be done with possible nutritional counseling and supplementation if needed," she told

"This study did not state that vitamin B12 deficiency causes preterm birth," Dr. Greves continued. "However it was associated with a higher chance of having a preterm birth." But women should be concerned enough about preterm birth to talk about their diets with their doctors and to "ensure that everything is being done to prevent and manage vitamin B12 deficiency." If necessary, a dietitian can work with an obstetrician to make sure expectant women are getting enough of the crucial vitamin.

"It is important to keep in mind that vitamin B12 deficiency is not just restricted to women who follow a vegan diet," Dr. Greves also cautioned. "There are also pregnant women affected by vitamin B12 deficiency if they have had gastric bypass surgery, Crohn's disease, ulcerative colitis, or other causes that could affect the absorption of vitamin B12 in their intestinal tract."

Melissa Willets is a writer/blogger and a mom. Find her on Facebook where she chronicles her life momming under the influence. Of coffee.