Final answer:
Engorgement is most likely to occur when the breast tissue becomes congested during lactation.
Step-by-step explanation:
Engorgement is most likely to occur when the breast tissue becomes congested. During lactation, milk moves from the alveoli through the lactiferous ducts to the nipple. When the infant suckles, sensory nerve fibers in the areola trigger a neuroendocrine reflex that results in milk secretion from lactocytes into the alveoli. The posterior pituitary releases oxytocin, which stimulates myoepithelial cells to squeeze milk from the alveoli so it can drain into the lactiferous ducts, leading to engorgement if the breast tissue becomes congested.