The let-down reflex (milk ejection reflex) is the physiological process by which the hormone oxytocin causes muscles in the breast to contract and propel milk through the ducts towards the nipple during feeding or expressing.
The let-down reflex, also known as the milk ejection reflex, is the mechanism by which milk is released from the breast during breastfeeding or expressing. The NHS explains that "your baby's sucking causes muscles in your breasts to squeeze milk towards your nipples" — a process it calls the let-down reflex. La Leche League GB identifies oxytocin as the key hormone involved: "Oxytocin is the hormone that triggers your letdown (milk ejection reflex)." Oxytocin is released in response to the baby sucking, to skin-to-skin contact, and to other sensory cues associated with the baby.
What does the let-down reflex feel like?
The NHS notes that sensations vary considerably between mothers: "Some women get a tingling feeling, which can be quite strong. Others feel nothing at all." The NHS also describes the change in the baby's sucking pattern as a reliable observable sign: "Their quick sucks will change to deep rhythmic swallows as the milk begins to flow." If the let-down reflex is very strong, the baby may cough or splutter as milk flows rapidly.
Can the let-down reflex be triggered spontaneously?
The NHS notes that the let-down reflex can be triggered without the baby at the breast: "Sometimes you'll notice your milk letting down in response to your baby crying or when you have a warm bath or shower. This is normal." When expressing, La Leche League GB recommends techniques to encourage the reflex, including looking at the baby or at pictures of them, gentle breast massage, warm compresses, and skin-to-skin contact, as these stimulate oxytocin release.
What can inhibit the let-down reflex?
La Leche League GB states that stress and anxiety can impede the let-down reflex: "even mildly stressful situations of feeling rushed can make it difficult to trigger a letdown when using a breast pump." La Leche League GB also notes, citing evidence, that alcohol is a profound inhibitor of oxytocin release, which inevitably reduces milk let-down and the amount of milk delivered to the infant.
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