Final answer:
Breast engorgement is caused by the accumulation of milk in the lactiferous ducts and glands, which can lead to swollen, hard, and painful breasts.
Step-by-step explanation:
The nurse can explain that breast engorgement is typically caused by the accumulation of milk in the lactiferous ducts and glands. This condition can happen when there is excessive milk production, a sudden stop in breastfeeding, or when the regular breastfeeding schedule is disrupted. This build-up of milk can cause the breasts to become swollen, hard, and painful. The lactation process involves the production of milk in the alveoli and its movement through the lactiferous ducts to the nipple. If the milk isn't expressed, either by a nursing infant or through other means, it can lead to engorgement.