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What is the Let Down Reflex?

Reviewed by Dan Brennan, MD on March 17, 2021

When your baby first latches on to nurse, they don’t actually get much milk at first. Instead, their suckling sends a message to your body to release the milk stored in your breasts. The strength and timing of the let down reflex, also called the milk ejection reflex, varies from mother to mother. 

How Does the Let Down Reflex Work?

If milk came out of your breasts instantly when your baby latched on, you’d probably leak constantly. Instead, your breasts store the milk until it’s needed. Most often, your let down reflex is triggered by a particular suckling motion your baby makes to stimulate milk production.

The let down reflex is a physiological response to your baby’s sucking. They stimulate small nerves in the nipple, which causes prolactin and oxytocin to produce milk and let down milk, respectively. The reflex is often accompanied by a tingling sensation in the nipple, but not all women experience that.‌

If you pay attention to your baby’s nursing patterns, at first their suckling will be faster and shallower to stimulate the release of milk. Once your milk lets down and your baby is drinking, their suckles will be deeper and longer. If they nurse longer and need more milk, they may adjust how they suck to stimulate more milk flow. 

Other let down triggers. Since your brain is wired to care for a newborn, other things may trigger the let down reflex. If your baby cries, or if you hear any baby cry, your milk may let down in response. If you go too long without nursing and your breasts get too full, your let down reflex may trigger to relieve the pressure.

Strong emotions may also trigger a let down of milk. If you are feeling intensely stressed, angry, or sad, your body may take that as a sign that you need to nurse your baby or release milk to alleviate pressure.

If your milk is not letting down, you can physically stimulate the nipple to allow let down. Try gently rolling your hand down your breast toward the nipple, then massage gently. It can also help to relax and think about your baby.

What Are Signs of a Good Let Down?

Breastfeeding is wonderful for your baby, but it is often full of doubts and questions. Are you producing enough milk? Are you doing it right? This extends to the let down reflex, too. You may wonder if your let down is strong enough or too strong. 

Here are signs of a healthy, functioning let down response:

Uterine cramps. You may notice that your uterus cramps during a let down in the days following birth. This is natural and nothing to be concerned about. As with menstrual cramps, for some the cramps are mild and barely noticeable, while for others the contractions can be more painful.

Change in sucking pattern. You may notice a change in your baby’s sucking pattern during a nursing session. Their suckle will go from being short and fast to long and slow once milk lets down. If they need more milk, their sucking may change again to encourage another let down.

Your feelings. Moms often report that they feel very relaxed and even sleepy when their milk lets down. This is a side effect of the oxytocin released during let down. You may also feel suddenly thirsty, which is your body’s way of preparing to replace the milk being removed during a nursing session.

Complications of the Let Down Reflex

Oversupply milk ejection reflex. A powerful let down is often accompanied by an oversupply of milk, sometimes called oversupply milk ejection reflex (O-MER). When your let down happens, you may notice that your baby sputters, coughs, and even chokes on your milk. Your baby may bite down to slow the milk flow. You may leak when not nursing or notice that your baby has more frequent but short feedings if you have an oversupply.

If this happens, keep a bib or cloth handy to catch your milk when it first lets down so that your baby doesn’t choke. After a moment when the let down slows, you can try latching your baby again. You can also restrict your milk flow by squeezing your areola during breastfeeding.

Talk to your doctor about safe ways to decrease your oversupply so that your let down is less strong.

Dysphoric milk ejection reflex. In some women, breastfeeding can create a negative physiological response, leading to negative emotions like guilt, anxiety, depression, and sadness. It is usually an isolated response that occurs only when you first let down your milk and into the first few minutes of breastfeeding. This is called dysphoric milk ejection reflex (D-MER) and is different from postpartum depression

There is still more research needed on the causes and effects of D-MER. Talk to your doctor if you are struggling with negative emotions during breastfeeding. 

Weak let down. You may have a weak let down if your baby seems frustrated while nursing. They may not be getting enough milk, or they may not be getting milk as fast as they want it. Using a breast pump can supplement less successful nursing sessions.‌

When pumping, look at photos and videos of your baby to try and encourage a let down. And just as you do when breastfeeding, try to relax. Take deep breaths and think about your little one, letting go of any stress.

Show Sources

SOURCES:

Attachment Parenting International: “Why Bedsharing and Breastfeeding Go Together, and What Could Happen When You Ignore Biology.”

Australian Breastfeeding Association: "Let-down reflex (milk ejection reflex)."

Clinical Endocrinology: “Thirst induced by a suckling episode during breast feeding and relation with plasma vasopressin, oxytocin and osmoregulation.”

Kids Health: “Breastfeeding FAQs: Pain and Discomfort.”

La Leche League International: “Oversupply,” “What is D-MER?”

Unity Point Health: “What is a let-down reflex?”

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