How does breastfeeding work?

In the last fifty years, much has been learned about breast milk, and about the process of breastfeeding, and it’s worth understanding this process better.

One of the first things to know is about breast size.

We know that breasts come in all different shapes and sizes – and that’s fine for making milk!

A lot of women feel concerned that they may struggle to make enough milk for their babies if they have small breasts.

Generally, that is not true at all. 

Whether you are large-breasted or small breasted, your body has all of the functioning ability to make as much milk as your baby needs, and this is still true no matter what size your baby is!

Baby laydown and breastfeeding

The external structure of the breast

The nipple is surrounded by the areola, the dark area around the base of the nipple, and has an excellent blood supply.

It also has sweat glands and sebaceous glands which lubricate the area too.

It also has Montgomery’s Tubercles, which we know alter the PH of the environment of the nipples, making the area hostile to bacteria.

It helps us to understand why it isn’t necessary to wash your nipples before or after feeding.

There is an antimicrobial effect going on there.

About 20 percent of breastfeeding women say that they have seen milk leaking out of Montgomery’s Tubercles, which look like little bumps around the edge of the areola.

Don’t worry, it’s completely normal.

The internal structure of the breast

If you were to look inside the breast, you would see between four to seventeen structures called lobes, and each lobe looks like an upside-down bunch of grapes. 

Each central stalk from the ‘bunch of grapes’ will lead to a hole at the end of the nipple (nipple pore).

So if you have four lobes in your breast, you’ll have four pores at the end of your nipple. If you’ve got seventeen, you’ll have seventeen pores. 

Thinking about each grape-like structure, imagine the skin of the grape being made up of many cells.

Breast milk is made in these cells, and then stored within the grape-like structures, of which there are hundreds of them within each breast!

Surrounding each grape-like structure is a meshwork of muscle cells. Under the action of a hormone called oxytocin, every one of the muscle cells will contract simultaneously, and this will cause all of the grape-like structures to contract at the same time, sending milk out towards the nipples.

That is called the ‘let-down’ of milk.

While you are pregnant, the milk-making machinery inside your breast, these lobes begin to grow and proliferate.

There’s also an enormous blood supply which increases too, and the blood supply comes and surrounds each of these grape-like structures.

Raw materials from your blood will be taken from there, and a new substance, breast milk is made. 

Older baby breastfeeding with mum

Not everything that is in your blood gets into the breastmilk. Breast milk is a unique, NEW living and active substance, but it needs raw materials that come from the blood supply.

Inside your breast, there is fat that helps to protect the structures inside and the connective tissue.

There’s also a substance called lymph, which helps to take waste away from the breast through the lymphatic system.

A lot of breastfeeding women are surprised to learn that their body has been producing a milk called colostrum (a low-volume, sticky type of milk) from sixteen or seventeen weeks of pregnancy.

This milk is made in these structures already mentioned.

While you’re pregnant, you have a very high level of a hormone called prolactin, and this is the milk-making hormone.

However, due to the action of other hormones present, while you’re pregnant, prolactin will be inhibited – therefore, only a small volume of milk is made at this stage.

Once you’ve given birth, and particularly, once the placenta has been delivered, the hormone levels that were inhibiting prolactin, fall dramatically, the prolactin hormone levels increase, and this, in turn, increases the volume of milk, which usually starts to kick in about 30 to 40 hours after giving birth.

Before this point, the milk that you were making was driven solely by hormones, and this means that even if you weren’t going to breastfeed, you would still be aware that milk was being made in your body, and was available.

After this point, the milk will be made according to how much emptying of the breast happens.

That means your baby needs to be frequently feeding, according to his needs, to generate the necessary milk supply.

Close of of a baby breastfeeding

It’s very much about demand and supply.

When your baby puts in demand for milk at the breast, your body makes more.

When there is emptying going on, – i.e., every time a little bit of milk comes out of the breast as your baby swallows, your body will then make more on that particular breast.

That is the mechanism that works throughout your breastfeeding journey, and right until you stop breastfeeding.

With this in mind, know that when your baby starts to feed more frequently at the breast – which can often happen during growth spurts or cluster nursing, or illness, etc., your body will begin to make more milk and as more demand goes in, your baby gets more. 

The opposite is also true. When there’s less emptying of the breast, your body will make less, which is also normal. 

Many breastfeeding women worry about the amount of milk that they are producing at the beginning – but it’s realistic to expect minimal amounts.

Your baby’s stomach size is the size of a marble on day one, so he doesn’t need a large volume of milk.

Even by day three, your baby’s stomach is only the size of a shooter marble, which isn’t much bigger than a regular marble.

By 10 to 14 days, it will be the size of a golf ball, between 65 to 80ml – so babies don’t need high volumes of milk!

Please don’t be alarmed if you find that in the first couple of days, particularly, you are only producing tiny teaspoon size amounts of milk.

From day two to three after the birth, you will begin to see that your milk supply is increasing as the composition of your milk changes.

The higher levels of sodium, chloride and protein that were in the colostrum, tend to reduce, while lactose and other nutrients start to increase.

When your baby feeds at the breast, and has a good feed, and comes off the breast looking quite full – your breast will not be empty.

While frequent feeding is happening, there is always about 25% residual milk in the breast at any given time.

#You don’t have to wait for your breasts to refill, because as milk comes off the breast, your body makes more.

There is a factory scenario going on, so there will always be available milk.

The more drained your breast is, the rate of milk production will be faster.

Lady in a purple top breastfeeding her baby

The less drained, the rate will slow down. The more drained your breast, the higher the concentration of fat at that point, because of the low volume. The opposite of that is also true.

So the rule of thumb is to allow your baby to feed as often and as frequently as he wants, and be assured that he’ll get all the breast milk and all the nutrients that he needs.

We know that every time a little bit of milk comes out of the breast, your body makes more on that side, and as your baby gets more and your body produces more. So how does that work?

Your baby comes to the breast and does fast sucks at the beginning of the feed.

Those rapid sucks send nerve impulses to the brain that will cause the pituitary gland (in the brain) to release hormones, oxytocin, and prolactin.

These hormones, particularly oxytocin, will act on those muscle cells around the grape-like structures.

It’s the action of prolactin that causes the contraction of those structures, and the let-down of milk.

The milk will come shooting down a whole network of ducts leading to the holes at the end of the nipple.

The milk will come out of the nipple and hit the back of your baby’s throat. When babies feel milk hitting the back of the throat, they start to swallow.

Your baby will then change his pattern – it will generally be a lot slower and more rhythmical with sucking, swallowing, and pausing.

Baby held in arms being breastfed

Some of you may feel the let-down as a tingling.

Some feel it a little bit sharper than that at the beginning, but it usually settles down after a couple of weeks. Some of you will never feel it at all, which is also fine.

Listen out for the sound that your baby makes when swallowing, which is a far more important sign.

After your baby has swallowed the milk from that batch, he will need to change his pattern again. 

At the end of the let-down the volume is very low, and many babies do a little bit of flutter suckling, then work hard again to ‘call’ another let-down of milk.

Your body may produce three to five let-downs (on average) on one side if your baby works hard.

It’s also worth considering breast storage capacity.

While some women with smaller breasts have unnecessary concerns about not being able to produce enough milk, what it can mean is that your breasts are not able to store as much milk between feeds.

Small breasts may mean that your baby may feed more frequently, but be encouraged that your body can generally make all the milk that your baby needs, irrespective of the size of your breasts.

Larger breasted women may have a greater storage capacity, and the baby may be able to go longer between feeds – but once again, the body will make what the baby needs.

So from birth, every day, your baby ‘tells’ your body to make milk. Your baby grows rapidly in the first month or two after the birth, so every day your baby needs extra calories. 

Your body will make that little bit more every single day.

However, the amount you make will generally plateau at about one month, and it will produce a very similar amount after that, with that similar amount continuing up to six months.

It doesn’t really fluctuate that much, apart from the odd growth spurt.

The frequent intensive feeding that happens over the first few weeks after birth takes a lot of breastfeeding mothers by surprise.

This period can feel so intense, tiring, and relentless, but this is normal in biology.

Once you’ve got past that first four to six weeks, things do tend to settle down, although patterns will keep on changing.

Finally, be assured that your supply is always in a state of flux at any given time.

Breasts work independently as well, and some women have breastfed from only one side for months.

Your body can do that as well, but know that there will be dips in supply at times, and there will also be increases, and you can boost your supply, or you can deliberately reduce your supply if you want to.

The more you understand the mechanism, the more your confidence can grow to help you move forward with breastfeeding confidently.

Review dates, references & further resources

Review Dates

Version 1.1 published in March 2019. Next review date: Jan 2022


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