The body needs vitamin B12 to form healthy red blood cells. When a pregnant woman doesn't get enough vitamin B12 from her diet, her body can't produce enough healthy red blood cells. Women who don't eat meat, poultry, dairy products, and eggs have a greater risk of developing vitamin B12 deficiency, which may contribute to birth defects, such as neural tube abnormalities, and could lead to preterm labor.
Vitamin B-12 is also a necessary vitamin for the body to have to help with the production of red blood cells. Although some women may consume enough B-12 in their diet, it is possible their body cannot process the vitamin, and this causes them to have the deficiency.