I have read this from the site of the vegan society... Hope this would help some parents who is raising vegan babies...
Up to the age of four to six months, the diets of many infants of vegan and of non-vegan parents are identical. The perfect food for the young infant is breast milk and supplementary foods should not be introduced until after four to six months of age. Breast-fed infants of well nourished vegan women tend to grow and develop normally(11). The infant receives many benefits from breast feeding, including some immune system enhancement, protection against infection, and reduced risk of allergies(12). Moreover, as human breast milk is the natural food for baby humans it also probably contains substances needed by growing infants which are not even known to be essential and are not included in infant formulas. Meanwhile, nursing mothers derive benefits such as reduced risk of premenopausal breast cancer, release of stress-relieving hormones and, for some, sheer convenience (12). For all these reasons, we strongly encourage breast feeding.
Vitamin B12 and vitamin D are key nutrients for a young infant being exclusively breast fed by a vegan woman. Mothers whose diets contain little or no vitamin B12 will produce milk with very low levels of vitamin B12 (13). As this vitamin is important for the developing nervous system, it is crucial for the infant to have a reliable source of vitamin B12. Some vegan women opt to use a vitamin B12 supplement while others rely on fortified foods such as some breakfast cereals, fortified yeast extracts, non-dairy milks and some soya products in order to meet both their own and their baby’s need for vitamin B12. If the mother’s diet does not contain a reliable daily source of vitamin B12, the child itself should receive a daily source of vitamin B12.
The vitamin D content of breast milk varies with the mother’s diet and her sun exposure, although vitamin D levels in breast milk are usually quite low. All children below three years of age have a high requirement for vitamin D to enable calcium deposition in bone. The Department of Health therefore recommends that vitamin drops containing vitamins A, C and D be used for all children from 6 months to 5 years of age, whether vegan, vegetarian or omnivore. Welfare vitamin drops, which are available at low cost, or free to certain families, contain no animal products and are suitable for vegans.
Readers may also have heard of docosahexaenoic acid or DHA, a fatty acid which appears to be important for eye and brain development and is found primarily in animal foods. However, vegans can make DHA from another fatty acid called alpha-linolenic acid, which will be contained in the breast milk if the mother’s diet includes good sources such as flaxseed oil, ground flaxseed and rapeseed oil. Reducing the use of other oils such as corn oil, sunflower oil, and safflower oil and limiting foods containing hydrogenated fats will also help the breast fed infant to make more DHA. These oils contain linoleic acid and hydrogenated fats contain trans-fatty acids which interfere with DHA production.
If breastfeeding is not possible or is contraindicated, there is just one formula feed suitable for vegan infants: Vegan Society trademark holder Farley’s Soya Formula by Heinz. On no account should soya milk, nut milk, rice milk, oat milk, pea milk or other home-prepared “formulas” be used as these do not contain the appropriate ratio of nutrients and can lead to potentially life-threatening conditions.