How feeding works

We’re talking all about pumps and pumping in this guide. To do that well, we need to understand what a pump is there to do, which is remove milk from your breast by mimicking a baby (as best it can).    

What does a baby do to feed at the  ?

A healthy baby uses their jaw to suck and compress to remove milk from the breast. But it’s not quite how you might first imagine it.

Here’s what is happening when a baby once latched, is suckling well.

Image of baby opening jaw






Image of baby drawing nipple back

Image of baby compressing nipple

Lowering the jaw to create suction

Pulling the nipple back and pulling milk out of the nipple

Compressing to slow flow to swallow and breathe

A baby creates suction (a.k.a vacuum or negative pressure for physics nerds out there) by lowering her jaw. That suction helps to pull back the nipple, which draws milk out of the nipple into the baby’s mouth. She then compresses the breast with her jaw, and the ducts of the mammary gland within it, which stops (or slows) the milk coming out of the nipple and allows her the swallow the milk in her mouth and open her airway to breathe.

So it’s not her closing her jaw that draws out your milk, it’s opening it.

It seems counter-intuitive but think about a baster from the kitchen. You put the long tube into the sauce, then you squeeze (compress) the bulb at the top. The liquid doesn’t actually run up the tube until you release the bulb. That’s because you’re creating suction by opening up the bulb.

By opening her jaw, your baby is ‘releasing the bulb’ and creating suction to draw out your nipple and milk.

How do we know all of this?

The science of milk ‘removal’ or ‘extraction’ has been studied for some time. Scientists and clinicians have looked at the biomechanics of sucking and breathing patterns of babies feeding at the breast and the bottle. Some studies have observed babies feedin and others have even used ultrasound to try to see what’s going on inside the breast and baby’s mouth[4]. Until the ultrasound studies, there was some disagreement about how infants actually transfer milk from the breast[5], but that seems to have settled now. The next focus for research looks to be  

Ultrasonography of breastfeeding pairs demonstrates that milk transfer occurs in response to the intraoral vacuum generated by reflex downward excursion of the jaw, at the same time as the mammary ducts contract with milk ejection. The infant tongue moves downward as a single unit in tandem with jaw depression (Douglas & Geddes, 2017; Geddes & Sakalidis, 2016).[6]