Let-down is the process by which milk is released from the milk glands to the milk ducts in preparation for breastfeeding. When a breastfeeding woman's breasts are stimulated by suckling or pumping, the pituitary gland produces the hormone oxytocin, which triggers the let-down reflex.
Signs of let-down include:
A tingling sensation in the nipples, sometimes with mild pain.
Milk leaking from the breast before nursing or pumping, or leaking from one breast while the baby is nursing at the other breast. Some women may experience let-down when they hear a baby cry.
Uterine cramps during nursing.
Increased vaginal bleeding during or just after nursing or pumping the breasts.