How Does Breastfeeding Work? An Explanation

How Does Breastfeeding Work? An Explanation

Most mothers can make plenty of milk for their baby or babies.

Getting breastfeeding off to the best start possible helps establish a good supply.

Once established, your milk supply is robust and in most cases you can keep making milk indefinitely as long as it’s removed well and often enough.

Nonetheless, it’s common for breastfeeding mothers to worry about their milk supply.

Even before a baby is born some mothers worry if they’ll be able to make enough milk.

When it comes to figuring out whether your baby is getting enough milk or not, it’s important to rely on reliable signs and not the unreliable signs.

Having an understanding of how breastfeeding works can help you feel more confident in your ability to make plenty of milk for your baby or babies.

How Does Breastfeeding Work?

So, how does breastfeeding work? It all begins midway through pregnancy.

During Pregnancy Your Breasts Start Making Colostrum

The first milk your breasts make is colostrum. Colostrum is a thick yellow coloured fluid and a concentrated source of immune protective factors, protein and minerals. Your breasts start making colostrum from about half way through pregnancy.

During pregnancy, you have high levels of the milk-making hormone, prolactin, in your bloodstream. However, you don’t make large volumes of milk during pregnancy as there are also high levels of the hormone progesterone. Progesterone ensures the volume of milk you make remains low.

The Milk Volume You Make Increases Once Your Baby Is Born

With the birth of your placenta (third stage of labour), your progesterone levels plummet. This allows prolactin to then kick start the process of making larger volumes of milk from about 30-40 hours after birth.

Before this point, the milk you make is driven by hormones. After this point however, the amount of milk you make is determined by how much milk is removed (see ‘Supply Equals Need’ below).

Even though the onset of making larger volumes of milk begins 30-40 hours after birth, it typically takes a little longer before most mothers feel their breasts making larger volumes of milk and their milk coming in.

So, how does milk get removed from your breasts?

The Milk Ejection Reflex (Let-down Reflex) Makes Milk Available To Your Baby

Your baby suckling at your breast stimulates nerve endings. This causes the hormone oxytocin to be released into your bloodstream. Oxytocin then makes the muscles around the milk-making (glandular) tissue in your breasts contract, pushing the milk into the milk ducts, and out through the nipple openings in your nipple. This process is known as the milk ejection reflex and it’s what makes your milk available to your baby.

Not all mothers feel their milk ejection reflex. For some mothers, the only way they can tell this reflex occurs is due to the change in their baby’s sucking. At the start of the feed, a baby does a quick shallow sucking. Then when this reflex occurs and the baby starts getting a flow of milk, his sucking changes to deep rhythmical sucking with swallows.

Other mothers feel their milk ejection reflex. For example, they may feel:

  • A tingling sensation in their breast
  • A slight prickling or pain in their breast
  • Milk leaking from the other breast (as the reflex occurs simultaneously in both breasts)
  • A feeling of thirst
  • A tightening of their uterus

The more often your baby feeds, the more milk ejection reflexes occur, and the more milk gets removed from your breasts. The more milk that gets removed from your breasts, the more milk your breasts will make. That is, your breasts make milk on a supply equals need basis.

Breastmilk Production Works On A Supply Equals Need Basis

Feeding your baby when your baby needs to be fed (i.e. when he shows feeding cues) helps ensure he gets the milk he needs.

The more milk that gets removed from your breasts, the more milk your breasts will make.

Whereas, the less milk that gets removed form your breasts, the less milk your breasts will make.

Supply and demand can sound simple, but it can also lead to more questions. Are your breasts ever empty? Do you need to wait a certain period of time for your breasts to fill up before feeding your baby again?

Your Breasts Are Never Empty

It’s important not to wait for your breasts to ‘fill up’ before feeding your baby. Breastmilk is continually being made. In fact, your baby drinks an average of only 67% of the available breastmilk each feed.

The more drained a breast is, the faster the rate more milk is made. Whereas, the less drained a breast is, the slower the rate more milk is made.

Also, the more drained a breast is, the greater the concentration of higher-calorie/higher fat-rich milk in that breast. The less drained a breast is, the greater the concentration of lower-fat/lower-calorie milk in that breast.

Feeding your baby when your baby need to be fed helps ensure he gets the breastmilk he needs. Therefore you need not worry about ‘foremilk’ or ‘hindmilk’.

Another factor that influences milk production is your storage capacity.

Different Mothers Have Different Storage Capacities

Storage capacity refers to the amount of milk a breast can store between feeds. Storage capacity differs greatly between mothers and also differs between breasts of the same mother. Mothers with either large or small storage capacities can both produce sufficient milk for their baby.

A baby whose mother has a larger milk-storage capacity may be able to go longer between breastfeeds. A mother with a smaller storage capacity will have breasts that fill up quicker and so she will need to breastfeed her baby more frequently to maintain her milk supply (by keeping her breasts well drained) and to satisfy her baby’s needs.

Again, feeding your baby as often as your baby needs helps ensure he gets the milk he needs.

But how much milk do breastfed babies typically need?

A Breastfed Baby Drinks A Similar Daily Volume Between 1 And 6 Months

After the initial rapid increase in breastmilk consumption in the early post-partum period, consumption levels out. There is wide variation for when this levelling-out occurs but typically it’s somewhere between about one week and one month.

The volume of breastmilk consumed when this levelling-out occurs varies from baby to baby. What research tells us, however, is that for an exclusively breastfed baby between the ages of 1 and 6 months, the average volume consumed in 24 hours is 788mL (range being 478mL to 1356mL).

The only precise way to help ensure your baby gets the right amount of milk he needs is to breastfeed him when he needs to be fed (provided he removes milk well).

Now that you have a better understanding of how breastfeeding works, hopefully you feel more confident in your body’s ability to help your baby grow and develop in the way nature intended.

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Renee Kam is a mother of two daughters, an International Board Certified Lactation Consultant (IBCLC), a physiotherapist, author of 'The Newborn Baby Manual' and an Australian Breastfeeding Association Counsellor. In her spare time, Renee enjoys spending time with family and friends, horse riding, running and reading.


  1. Hi Renee! What if I want to increase supply for my left breast and decrease supply for my right breast? I have been breastfeeding for a month now. I tried to pump both and only got 50 ml from the left breast and 120 ml from the right.

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