How does breastfeeding work?

Anatomy of the breast 

It might be helpful to look at the structure of a breast to understand how breastfeeding works.

^{Image by: Dr Gabriella Cichonska}

The areola is the dark circle around the nipple. This often becomes darker during pregnancy; to help the baby find it to feed!

The bumpy bits on the areola are called Montgomery tubercles. These make an oily substance that lubricates the nipple. It smells like amniotic fluid (the fluid which surrounds your baby as it grows in the uterus) which is familiar to the baby. 

Muscle cells (myo-epithelial cells) help squeeze breastmilk from the back to the front of the breast.

Milk ducts are little structures that direct breast milk from the back of the breast to the front. They store and deliver milk to the outside world via nipple pores.

Alveoli are little sacs with milk producing cells (lactocytes) in them. Milk is stored and produced here.

Breasts can be many shapes and sizes. As long as there are enough milk ducts, milk can be made to breastfeed¹. 

Breasts start to develop during puberty (usually around the age of 12-13 years). With each period, hormones are released. This causes a build-up of fatty tissue and milk ducts. These will help when it’s time for milk lactation. 

What is lactation? 

Lactation is the process of making and then releasing milk – let’s look in more detail.

How is human milk produced (lactogenesis)? 

In the first half of pregnancy, breasts increase in size with growth and development of more milk ducts and alveoli. 

Lactogenesis has four stages. 

Lactogenesis one

Colostrum starts being made at around 15-16 weeks of pregnancy. Women may start leaking small amounts of breastmilk at this time. 

Two hormones are also released:

1) Oestrogen which encourages milk ducts to be made.

2) Progesterone which encourages alveoli to develop. It also stops milk being removed until it’s needed; acting like the brakes in a car². 

Once a baby is born, it is all systems go. You can feed as soon as you are both ready. Once the placenta is delivered, progesterone is switched off. The brakes of the car are lifted and it’s time to make lots of milk.

Lots of skin to skin contact will allow baby to follow their natural feeding instincts. It will also encourage prolactin (the milk making hormone) to kick into gear³.

When the baby feeds, it will send a signal to your brain. This will switch on two hormones:

1) Prolactin which encourages the breasts to make more milk.

2) Oxytocin which encourages milk to be squeezed from the breast. This is sometimes called the ‘let down’ and is often described as a tingling sensation around the nipple⁴. 

Lactogenesis two

This occurs about two to three days after the baby is born. 

Prolactin levels rise and lots of milk is made. This is sometimes called your ‘milk coming in’. Breasts rapidly increase in size and can be warm and tender. Your body is trying to figure out how much milk your baby needs. Over the next few weeks, you will work this out together. 

Lactogenesis three 

This starts around nine days after birth and continues as long you choose to breastfeed. This is the maintenance phase. If the baby feeds, more milk is produced. If the baby does not feed as much, less milk is produced⁵. 

 Lactogenesis four 

Stag four happens about 40 days after your last breast feed. Milk production tails off and eventually stops. This is called involution. 

How do I stop lactating if I want to? 

If you want to reduce or stop breastfeeding, it might be easiest to cut down one feed at a time. If you stop suddenly, you might develop sore breasts or even mastitis. 

It’s important to look after your milk supply. If you are thinking of combination feeding (replacing a breastfeed with a bottle of formula), try and wait (if you can) at least six to eight weeks to avoid a drop in supply.

If you are thinking of reducing or stopping breastfeeding in a baby over one, do so in your own time; there is no right or wrong answer.⁶ 

Do you get a period while breastfeeding?

If you are exclusively breastfeeding, you probably won’t have a period for the first three to six months. This is called lactational amenorrhoea. 

If a baby feeds regularly, it sends a signal to your brain to stop the hormones being released that would usually make you release an egg and have a period if the egg isn’t fertilised.

Lactational amenorrhoea can be a great choice of contraceptive method when you do it properly. It isbe up to 98% effective at preventing pregnancy. 

You need to follow these rules to make sure lactational amenorrhoea is effective:

1. Breastfeeding at every 4 hours in the day and every 6 hours in the night 

2. Have no periods. A period after birth is a bleed for 2 days or more, 2 months after the baby is born. 

3. Your baby is less than 6 months⁷. 

Can you lactate even when you aren’t pregnant? 

Yes, there are several medications and conditions which mean a woman (or man) can make breast milk even when they aren’t pregnant. If this is happening, please get advice from your GP as soon as you can⁸.

It is important to mention, mothers who wish to adopt, can induce lactation with medication and stimulation of the breasts with a pump.

Hopefully this round up of how breastfeeding works is helpful. And please remember that if you’re interested in breastfeeding or are trying to breastfeed and need support – there is lots out there so make sure you reach out.