A vitamin B12 deficiency in infants is rare, but may sometimes be seen in breastfed babies of strict vegetarian mothers. Vitamin B12, also known as cobalamin, is only found in meat and other animal products. Most babies have a sufficient supply as long as the mother was not deficient herself.
Since vitamin B12 is only found naturally in animal products, vegetarian women who consume only plants may become deficient. Some mothers can pass along this deficiency in the womb if they do not take a prenatal vitamin containing B12 or a separate supplement of this vitamin. After birth, if a strict vegetarian mother breastfeeds her baby and discontinues her own supplementation of vitamin B12, the baby may develop a severe deficiency of this vital nutrient.
An infant with a deficiency in vitamin B12 may become lethargic and experience retarded growth. She may also become anemic and display poor muscle tone. Deficient babies often experience developmental delays or regress with regard to previously met milestones. Symptoms often do not show up until 6 to 12 months of age, but the baby may become clinically deficient as early as 2 months old.
The easiest method of preventing a vitamin B12 deficiency in infants is for moms-to-be and lactating mothers to consume foods that supply it. Meat, poultry, fish, eggs, milk, cheese and yogurt all contain this nutrient. Some foods, such as cereal and soy, may be fortified with vitamin B12. Women who do not eat products containing this vitamin should take a supplement with B12 throughout the course of pregnancy and the entire time they are breastfeeding. During pregnancy, a woman needs 2.6 mcg of vitamin B12 and while lactating, she should get at least 2.8 mcg every day, according to the National Institutes of Health Office of Dietary Supplements. Feeding an infant formula containing B12 can also prevent this condition from developing after birth.
Treatment for a vitamin B12 deficiency in an infant involves immediate administration of B12 to the baby and the breastfeeding mother, according to a British study published in the "Journal of the Royal Society of Medicine." The infant and mother will each receive an injection of vitamin B12 containing 1,000 mcg or more of the vitamin, and the mother will continue to receive injections every month to raise her own stores. After the initial injection, the baby will often receive future vitamin B12 through food sources. In some babies, the neurological damage is significant enough that it does not resolve after treatment.
A baby born to a mother with sufficient B12 will normally have a personal supply that can last about 8 months, according to the Kellymom website. After this point, the baby should be receiving this nutrient through his mother's breastmilk, a fortified formula or newly introduced solid foods derived from animal products.