We know that a newborn’s immune system is not nearly as effective as an adult’s or even an older child’s, and that it takes many months before a newborn can fight off infection as well as someone whose immune system is fully matured. Nonetheless, you may be pleasantly reassured to know that newborns are much better protected against (or immune to) potential illnesses and diseases than you might otherwise think. This is because during pregnancy, disease-fighting antibodies made in the mother’s immune system are able to make their way across the placenta and into her baby’s body. Fortunately, these antibodies stick around for several months and are able to give newborns an added level of protection from many routine illnesses during this important time when they are not as able to effectively make their own antibodies. However, all good things must come to an end, and infants gradually get less and less benefit from their mothers’ antibodies—that is, unless they are breastfed.