Final answer:
The nurse should inform new mothers that breast milk production is initiated when their infant suckles, triggering the release of prolactin and oxytocin necessary for milk production and ejection.
Step-by-step explanation:
The nurse should tell new mothers who are breast-feeding that breast milk is produced when suckling stimulates the release of prolactin. This occurs through a positive feedback loop where the infant suckles on the nipple, sending nerve impulses to the mother's hypothalamus. This signals the pituitary gland to release prolactin into the bloodstream. Prolactin then travels to the mammary glands, stimulating them to produce milk, which further encourages the infant to continue suckling. Additionally, oxytocin is released, which aids in the milk ejection, or let-down, reflex.
This lactation process is crucial for providing the infant with nutrients for development and growth as well as immunoglobulins to protect against infections. The mother's mammary glands undergo changes during the third trimester to prepare for this, and once lactation begins, the composition of breast milk changes over time to suit the infant's developmental needs.