How does oxytocin help release milk during breastfeeding?

During breastfeeding, oxytocin plays a critical role in the milk-ejection reflex, often referred to as "letdown" or "the draught".12

When an infant begins to suckle, the stimulus triggers the pituitary gland to release oxytocin into the bloodstream. This hormone travels to the mammary glands, where it binds to receptors on specialized myoepithelial cells surrounding the alveoli. Upon binding, these cells contract, which forces milk out of the alveoli and into the milk ducts, making it available for the infant to extract.12

This process is highly responsive and can occur within seconds of an infant beginning to suckle. Furthermore, the release of oxytocin can be conditioned; for instance, the sound of a baby crying or other cues associated with nursing can trigger the reflex even before physical contact. Conversely, because the release of oxytocin is sensitive to the brain's state, factors such as stress, fright, or embarrassment can inhibit this reflex, potentially making it difficult for the infant to extract milk.21