A medical illustration video recently went viral depicting the breast milk letdown reflex, or what happens when a baby starts suckling at a mother’s breast. The Instagram video, created by @design_cells, has been liked more than 40,000 times—because it’s so beautiful. 

The video—and its virality—is a testament to just how magical the breastfeeding process can be. Once the baby latches, the suckling action sets off a cascade of events that results in the release of breast milk in the span of just seconds.

Related: 6 ways breast milk is basically magic, according to science

It’s a streamlined sequence of reactions that would be hard to improve upon, and it’s incredible to watch how milk is produced on-demand for a hungry infant. 

But if you, too, are getting those phantom letdown boob twinges after watching—don’t say I didn’t warn you. That sharp, tingling, squeezing sensation is such a distinct feeling that’s impossible to forget, no matter how distanced you are from your breastfeeding journey.

The depiction is a simplified version of a complex biological and neurological process, but it’s an important tool that illustrates the powerful connection between a mother’s body and brain and her baby. A similar image went viral for depicting the milk ducts inside a lactating woman’s breast, which were arranged to look like a flower. It was not anatomically correct, but empowering nonetheless in its demystification of the female body.

Here’s what happens during the breast milk letdown reflex

  • When your baby suckles, it triggers nerves in the nipple, which sends a signal to the pituitary gland in your brain, causing two primary hormones to be released in your bloodstream.
  • One of those hormones, prolactin, is responsible for milk production. The action of prolactin increasing in the blood is what causes the small sacs of milk-secreting cells in the breasts, called alveoli, to produce milk. 
  • The other hormone, oxytocin, sometimes called the cuddle hormone, is what actually triggers the breast to “let down” the milk. Oxytocin promotes bonding and attachment between mother and child, which is why frequent breastfeeding sessions in the early days are so important. 
  • In the breast, the alveoli fill with milk, and when oxytocin triggers the let-down, the interwoven muscle cells surrounding the alveoli contract (hence that tingling feeling!) and the ducts fill with milk and flow out of the nipple to feed your suckling babe. Practically magic! 

Related: It’s science: breastfeeding can deepen mom’s bond with baby—for years to come

6 tips to know about the milk letdown reflex

  • During the first few weeks after birth, the more a baby latches to the breast, the more prolactin is produced, which helps establish milk supply. 
  • A baby’s suckling also triggers the release of additional hormones such as follicle stimulating hormone (FSH), luteinizing hormone (LH) and gonadotrophin releasing hormone (GnRH) that result in the suppression of ovulation and menstruation. That’s why exclusive breastfeeding for about six months can be considered an effective form of birth control, though night feeds are essential to keeping ovulation suppressed. 
  • Oxytocin can be released before a baby even latches on for a feed—it can also happen when the mother expects a feed to happen based on the infant’s regular feeding schedule. Oxytocin is produced more quickly than prolactin, so oxytocin works to release the milk that’s already in the alveoli, which is why your breasts may start to leak if you skip a feed or a pumping session.
  • Prolactin is responsible for producing milk to be ready for the next feeding. 
  • Smelling your baby, seeing a photo of your baby, hearing them cry or even just thinking about your sweet babe can also trigger the release of oxytocin—which can be a helpful way to encourage letdown when you’re away from your infant and pumping. 
  • If you’ve ever started to lactate after hearing a baby cry that’s not yours—or a phantom baby cry—that’s normal, too. Crying is an auditory cue can be a potent trigger for letdown. 

Related: Breastfeeding mama goes viral for leaking during a TV show theme song: “What is happening” 

What to do if you have a painful letdown

A painful letdown or milk ejection reflex (MER) can mean there’s an underlying issue at hand. Seek help from your doctor, midwife or a lactation consultant to get to the root cause, as you may be dealing with mastitis, an oversupply or thrush. Letdown can feel tingly and like a slight squeezing sensation, but it shouldn’t hurt.

Related: When breastfeeding hurts: 7 possible causes and solutions

On the other hand, not feeling the letdown doesn’t necessarily mean something’s wrong. You might start to notice it less after the first few weeks of feeding, or you may only feel it if a feed or pumping session has been delayed and there’s an abundance of milk collecting in your breasts. 

In rare cases, some women will experience depression or anxiety or anger right before letdown occurs, in a phenomenon known as dysphoric milk ejection reflex (D-MER). The condition is not considered a postpartum mood disorder because feelings subside a few minutes after letdown occurs. It seems to be related to a physiological response caused by the inhibition of the brain chemical dopamine just before milk let-down. 

Reach out to your child’s pediatrician or a lactation consultant to talk through questions or concerns, but remember, if breastfeeding isn’t working for one of you, it isn’t working for either of you. 

Related: Does breastfeeding make you sad, mama? You might have D-MER 


Deif R, Burch EM, Azar J, et al. Dysphoric Milk Ejection Reflex: The Psychoneurobiology of the Breastfeeding Experience. Front Glob Womens Health. 2021;2:669826. Published 2021 Oct 29. doi:10.3389/fgwh.2021.669826

Scatliffe N, Casavant S, Vittner D, Cong X. Oxytocin and early parent-infant interactions: A systematic review. Int J Nurs Sci. 2019;6(4):445-453. Published 2019 Sep 12. doi:10.1016/j.ijnss.2019.09.009

World Health Organization. Infant and Young Child Feeding: Model Chapter for Textbooks for Medical Students and Allied Health Professionals. Geneva; 2009. SESSION 2, The physiological basis of breastfeeding.

A version of this story was originally published on Aug. 9, 2022. It has been updated.