Definition

The process of making and secreting milk from the mammary glands in the breasts. Lactation usually begins during pregnancy when changes in certain hormones signal the mammary glands to make milk. After a person gives birth, the nipples release milk when a baby feeds from the breasts or when the person uses a breast pump. Lactation usually continues until milk is no longer being taken from the breasts. Lactation can sometimes be induced using certain hormone medicines in people who are not pregnant. Common factors that can affect lactation include hormone levels, certain medical conditions, breast surgery, injury to the breast or nipple, drug or alcohol use, and taking certain medicines.