Breastfeeding, or nursing, is the process of feeding an infant with milk produced in a woman’s mammary glands. The method has been linked with numerous benefits for both the nursing infant and mother.

Breasts are glands made of fatty tissue, glandular tissue, connective tissue, blood, lymph and nerves. During pregnancy, hormones stimulate the mammary glands (the glands in the breast that produce milk) to prepare for milk production. When a baby is placed at the breast of a woman who is lactating (producing milk) and begins to suck at the breast’s nipple and areola (the darker area of skin around the nipple), the action forces milk through tiny openings in the nipple. The amount of milk produced in the breast is directly related to the frequency of nursing. The breast is designed to keep up with the baby’s demand. 

For the first six months of life, babies should be fed only breast milk or infant formula. Both substances have almost all the nutrients a baby needs. At about six months, solid foods such as cereal can be introduced, but breast milk or formula (not cow’s milk) should be continued. Although both breast milk and formula provide nourishment to the baby, many experts recommend exclusively breastfeeding for the first six months of life, followed by partial breastfeeding beyond the first year of life. Breastfeeding is so widely encouraged because it offers a number of benefits to the mother and her infant.

Potential benefits for the baby include complete nutrition and protection from bacteria and viruses. For mothers, breastfeeding may lower the risk of certain cancers and bone disorders. However, breastfeeding requires a near constant time commitment and can result in certain complications, including sore nipples, engorgement (a condition in which the breasts feel hard and painful) and breast infection (mastitis).

In addition, there are certain conditions that make breastfeeding difficult or risky for the infant. For example, certain viruses (e.g., HIV, herpes simplex virus type 1 and type 2) can be transmitted from the mother to the baby through the milk. Some babies may have difficulty breastfeeding. This may occur with premature or low birthweight babies, or infants with conditions such as cleft lip or palate. Other times, a nursing mother may have difficulty establishing or maintaining adequate breast milk production due to extended pumping for a premature or ill newborn, maternal illness (e.g., hypothyroidism) or prior breast surgery. In some cases, a physician can prescribe medication (e.g., metoclopramide) to increase a woman’s milk supply. 

Women must also commit to certain lifestyle choices to breastfeed safely. Because many substances can reach the baby through the breast milk, nursing women should limit or avoid certain substances, including nicotine, caffeine and alcohol. In addition, some medications should not be taken while breastfeeding.