The benefits of breast-feeding are well established. Breast milk contains the right balance of nutrients for your baby, and the antibodies in breast milk boost your baby's immune system. But in some cases, exclusive breast-feeding isn't possible or practical.Breast-feeding for at least four months helps boost your baby's immune system. Breast-feeding throughout the first year is ideal.

Most breast-feeding mothers may wean their babies between ages 9 and 15 months.Milk has biologic specificity—meaning that every species of animal who breastfeeds their babies makes a milk that is unique for the young of that species.The amounts of nutrients change to match your baby's rapidly changing needs.

The germs in the baby's environment, to which the mother has been exposed, cause the mother to produce antibodies to that germ, which are passed on to the breastfeeding infant. An infant may be breast fed by its own mother or by another lactating female. Breast milk may also be expressed and fed to a baby through a bottle and pasteurized donor human milk may be used.