A. Breast milk provides the mix of nutrients that babies need for development. It supplies the right proportion of good proteins, carbohydrates and fats, including the omega-3 fats that may benefit a baby’s brain development. It’s believed that it also contains factors that support a baby’s immature immune system. What’s more, breastfeeding may help a woman return to her pre-baby weight. Six to eight of the pounds a woman gains during pregnancy are to ensure that she will be able to supply the energy needed to lactate: producing breast milk burns about an additional 500 calories per day.