(A) Mammary growth as well as milk production and maintenance in the breast occur in response to hormones produced primarily by the hypothalamus and the pituitary gland. (B) Prolactin stimulates the alveolar cells of the breast to produce milk. It is important in the initiation of breast-feeding. (C) Oxytocin, which is released by the posterior pituitary, stimulates the let-down reflex by contraction of the myoepithelial cells surrounding the alveoli. In addition, it causes contractions of the uterus and uterine involution. (D) Afterpains may occur with retained placental fragments. A boggy uterus and continued bleeding are other symptoms that occur in response to retained placental fragments.