Oxytocin is a hormone released from the pituitary gland in the brain. During pregnancy, oxytocin causes labor contractions to begin. Oxytocin also is released when a woman's breasts are stimulated by suckling or pumping, causing milk to move from the ducts and out the tiny holes in the nipple (let-down reflex). In the first few days after delivery, oxytocin also causes uterine contractions that help shrink the uterus back to its prepregnancy size.
After breastfeeding is established, your body may release oxytocin when you hear a baby cry, think of your baby, or have sexual intercourse. When this occurs, your breasts may leak milk whether or not you are actively breastfeeding or pumping.
Your body may not release oxytocin when you are anxious, embarrassed, or distracted. You may need to breastfeed in a relaxing, quiet, familiar, private place for let-down to occur.