Not achieving a “let-down,” or the flow of milk, can be frustrating and lead to concerns about milk supply and feeding efficiency. The let-down is the Milk Ejection Reflex (MER), the process that makes milk available to the baby or pump. When this reflex does not occur, milk is prevented from moving out of the breast. Understanding the biological and external factors can help resolve the issue.
Understanding the Milk Ejection Reflex
The milk ejection process is a reflex driven by hormones. When the nipple and areola are stimulated, nerve signals travel to the brain, prompting the release of oxytocin. This hormone travels through the bloodstream to the breast tissue, triggering the reflex. Oxytocin causes the tiny muscle cells surrounding the milk-storage sacs, called alveoli, to contract. This contraction forces the milk into the ducts, making it accessible to the baby or pump.
The other hormone involved is prolactin, which synthesizes milk for the next feed, not the current one. Prolactin levels increase after feeding or pumping, ensuring continued production. The let-down reflex relies solely on the rapid release of oxytocin. Because this reflex is involuntary and highly sensitive to external and internal conditions, changes in environment or emotional state can easily disrupt it.
Emotional and Physiological Inhibitors
The reflex often fails to engage due to a conflict between relaxation and stress hormones. When the body perceives a threat or is under duress, it releases catecholamines, such as adrenaline. Adrenaline directly inhibits the oxytocin release required for the reflex. This biological mechanism is a protective response, prioritizing immediate survival over feeding the infant.
Pain, such as from an unhealed incision or nipple discomfort, is a powerful stressor that triggers adrenaline release. Chronic sleep deprivation and fatigue also place the body in a state of stress, making it difficult for oxytocin to flow freely. Exposure to cold can hinder the process by causing vasoconstriction, which restricts blood flow to the breast tissue and interferes with hormone transport. Dehydration can reduce plasma volume, contributing to a suppressed hormonal response.
Mechanical and Procedural Factors
Adequate physical stimulation of the nipple and areola is necessary to send a strong signal to the brain. An improper latch during nursing provides insufficient stimulation, resulting in a weak signal for oxytocin release. A poor fit with pumping equipment can also impede the reflex. The breast pump flange must be sized correctly so the nipple moves freely without pulling in too much of the areola.
A flange that is too small can compress the milk ducts and cause pain, triggering the stress response that blocks let-down. Conversely, a flange that is too large may fail to provide the necessary friction and stretching required to signal the brain.
When pumping, start with the fast, light suction of the stimulation mode to mimic a baby’s initial rapid sucks. Inefficient milk removal due to incorrect suction levels or using worn-out pump parts can also prevent the full activation of the reflex.
Actionable Steps and Professional Support
To encourage the let-down reflex, focus on creating an environment that promotes relaxation and warmth. Applying a warm compress or taking a warm shower before a session can help. Relaxation techniques, such as deep breathing or guided meditation, counteract the effects of adrenaline.
Using sensory cues can help condition the reflex to start more easily:
- Looking at pictures or videos of the baby.
- Smelling a blanket the baby has used.
- Listening to the baby’s sounds.
- Performing gentle breast massage and nipple stimulation before and during the session.
If let-down issues persist, if pain is present, or if the baby is not gaining weight appropriately, seeking guidance from an International Board Certified Lactation Consultant (IBCLC) is recommended. An IBCLC can assess latch technique, evaluate pump fit and settings, and offer personalized strategies to support the milk ejection reflex.