How Does Breast Milk Develop?

Anatomy of the Human Breast

The human breast is made up of fatty tissues, lobes (which are milk-producing glands,) milk ducts, and connective tissue. If a normal, healthy woman becomes pregnant, then the series of changes in her body will signal the lobes to create milk and deposit them in the milk ducts. The baby, of course, can suckle the milk from the ducts and out the nipple.

Development

Dramatic changes take place in the breast for females during puberty. Various hormones are released during puberty that cause the body to mature. Estrogen is the hormone that most stimulates breast development during puberty. The changes that estrogen produces enable the breasts to make milk.

Pregnancy

Hormonal changes during pregnancy cause additional blood flow to the breasts, and the breasts become bigger. The nipples also become bigger and darker. These changes are the body's way to prepare to nurse a baby. During the third or fourth month of pregnancy, the breasts will start to make colostrum. Colostrum is a very thin form of breast milk, but it is full of antibodies and it is the first drink a newborn gets. As the pregnancy continues, some women's breasts will leak a little of the colostrum that is building up in them.

Motherhood

After the baby is born, his or her suckling stimulates the breasts to make milk. The milk is produced in the lobes, and flows down into the milk ducts and out the nipple. Most women will continue to produce breast milk as long as the child nurses. Mothers whose children wean gradually tend to stop producing milk just as gradually, and seldom feel the breast pain associated with an abrupt halt to breastfeeding.