How babies suck in breastfeeding

The tongue moves in tandem with the baby's jaw, which drops reflexly at the breast

The most important mechanism of milk transfer on the baby's part is the vacuum created by the jaw dropping down, bringing the tongue down with it. The tongue only needs to be able to reach the lower gum to be effective in breastfeeding, once fit and hold problems are taken care of.

So much of what you might hear about how babies suckle at the breast, and the various exercises you might be told you need to do on your baby to help with sucking skills, haven't been shown to be helpful when researched, and really don't make biomechanical sense for breastfeeding women and their babies.

A breakdown of what happens when your baby sucks, step by step

When your baby's mouth closes over your nipple and breast, the following things happen, if all is going well.

1. A seal is created so that air can't suck into your baby's mouth.

   • The lower half of baby's face buries into your breast, which creates the front part of the seal so that he can't suck air in from the environment.

   • His hard or soft palate and the middle of his tongue touch, which creates a seal so that he can't suck air into his mouth from his airways.

   • A slight baseline vacuum is created, which holds the nipple and breast tissue in your baby's mouth. If your baby has a lovely deep face-breast bury, which is what we're aiming for, you won't be able to see her lips.

2. Then, when your baby is at the breast, baby's jaw drops down reflexly, with the tongue following the jaw in tandem. This creates a much bigger vacuum inside your baby's mouth (because it is still sealed from the air). The vacuum applies mechanical pressure to the tissues inside your baby's mouth.

3. In response to the vacuum, your nipple and breast tissue

   • Are drawn further up into baby's mouth, and

   • Expand in all directions.

4. The mechanical force of the vacuum spreads evenly over the surface of the nipple and breast tissue inside your baby's mouth.

5. Each time the little jaw drops, more of your nipple and breast tissue is drawn into baby's mouth until it is as full as possible with breast tissue, and her mouth can no longer close up much at all between sucks. The more breast tissue that is drawn up by the vacuum as baby's jaw drops, the more her mouth is opened up wide by all that breast tissue. When her mouth is as full of breast tissue as it can be, the nipple will be drawn safely up onto the back of the tongue near where the hard and soft palate meet. Here the nipple is best protected from damage, and can heal.

6. At the same time, the sensory stimulation of baby's mouth on your nipple triggers a letdown. When your letdown occurs, the vacuum draws milk out from your milk glands and ducts. Milk is transferred into your baby's mouth because of both the vacuum, which is negative pressure, and the positive pressure of your letdown. You can find out about letdowns here.

That's how it all happens!

What doesn't happen when baby is suckling at the breast

• You might have heard that the baby's lips need to flange for successful breastfeeding, but this isn't the case. In fact, if you can see the baby's lips, the baby won't be transferring milk optimally. The lips need to be buried into the breast, with the lips and face together creating a seal so that a vacuum develops inside the mouth when baby's jaw drops.

• You can see that there is no reason to pull the breast back to look at what your baby's lips are doing - unfortunately, this will pull breast tissue out of his mouth, and he has to start over again drawing the breast tissue in incrementally deeper with his jaw drops.

• We know from ultrasound studies that the tongue moulds under and around the breast tissue during sucking, but breastfeeding does not require compression by, or a peristaltic movement of, the tongue.

• Healthy sucking also doesn't need the tongue to lift to half-way up the mouth or to move from side to side. Once the bolus of milk touches the back of the tongue and throat, the soft palate lifts and the bolus slides down between the soft palate and the back of the tongue into the oesophagus, with the swallow.

Recommended resources

• You can see a video and animation about how babies breastfeed here.

• You can find out about how baby's tongue works in breastfeeding here.

• You can find out about the role of bodywork in breastfed babies here.

• If you need help and would like to find a local NDC Accredited Practitioner, you can look here.

Selected references

Douglas PS, Keogh R. Gestalt breastfeeding: helping mothers and infants optimise positional stability and intra-oral breast tissue volume for effective, pain-free milk transfer. Journal of Human Lactation. 2017;33(3):509–518.

Douglas PS, Geddes DB. Practice-based interpretation of ultrasound studies leads the way to less pharmaceutical and surgical intervention for breastfeeding babies and more effective clinical support. Midwifery. 2018;58:145–155.

Douglas PS, Perrella SL, Geddes DT. A brief gestalt intervention changes ultrasound measures of tongue movement during breastfeeding: case series. BMC Pregnancy and Childbirth. 2022;22(1):94. DOI: 10.1186/s12884-12021-04363-12887.