Final answer:
Breast engorgement in postpartum women is caused by accumulation of milk in the lactiferous ducts. Signals from the baby's suckling cause the release of prolactin and oxytocin, which stimulate milk production and release.
Step-by-step explanation:
Breast engorgement in postpartum women is caused by accumulation of milk in the lactiferous ducts. During the third trimester of pregnancy, the mammary glands prepare for lactation by developing branching lactiferous ducts and alveoli lined with milk-secreting cells. When the baby begins suckling at the breast, signals are sent to the hypothalamus causing the release of prolactin and oxytocin, which stimulate the production and release of milk. The milk then accumulates in the lactiferous ducts causing breast engorgement.