Expressing & Storing Milk

Why Express Milk?

Expressing Milk

Storing Milk

Why express milk?

There are several reasons why you might need or want to express milk for your baby. These include:

when a baby can’t breastfeed
to make more milk
a return to paid work
separation
choice

When a baby can’t breastfeed

Babies and parents have many instincts for breastfeeding, but it is still a learned skill that can take time and practice. When babies won’t breastfeed, it is usually because they can’t. This could be for many reasons, for example:

they are preterm
they are unwell
they have a tongue tie
they are sleepy as a result of birth medications
they had a difficult birth
it is taking time to learn how to breastfeed

Expressing milk when your baby cannot nurse – or nurse effectively – protects your milk supply and provides milk to feed them. Breastmilk is especially important for babies who are unwell and/or preterm as it helps protect against illness and infections, and is ideal for a baby’s sensitive and immature digestive system.

Expressing milk is often a short-term solution. However, some mothers may find themselves exclusively expressing breast milk (‘exclusively pumping‘) long-term when their baby is ill or has medical difficulties.

Making more milk

Once your baby is born, milk production works on a supply and demand basis: the more milk you remove, the more milk you are likely to make. The first two weeks are very important. If not enough milk is removed early on, it may affect your long-term supply, and your baby may not gain weight as expected.

Some parents have underlying conditions that are risk factors for low milk supply. However, it is usually possible to make more milk. The main way to do this is by removing milk frequently, and for some parents this will include expressing.

A return to paid work

There are many ways to combine working and breastfeeding. It is not always necessary to express milk when returning to work. It may depend on:

the age of your baby
the length of time you are apart
your willingness – and ability – to express; pumping is not effective for everyone, although there are ways to improve this.
your baby’s willingness to take your milk when you aren’t there

Many mothers express initially for reassurance and comfort, and to avoid blocked ducts and mastitis. However, you may find that your body quickly adjusts to a new breastfeeding pattern and you no longer need or want to express.

Separation

You and your baby may need to be apart. This may be for illness or health reasons, an appointment or event, or a night away.

Your baby has an intense need for your presence as well as your milk, and separation can be hard for both of you. It may be possible to take your baby with you – young babies are very portable and often enjoy being out and about.

Choice

Some mothers choose to express milk some or all of the time. You might want – or feel pressured – to let a partner or other family member feed your baby. Some parents choose to exclusively pump because they don’t enjoy breastfeeding, but want their baby to have the benefits of their milk.

There are many ways partners and family can bond and be involved with a baby. Expressing milk takes time and energy.

Any breastmilk is good; however there are differences between a baby feeding at the breast and drinking breastmilk by a different method, for example from a cup or bottle.

Expressing Milk

What kind of pump do I need?

Pumps are available to hire and to buy. The pump you use depends on your reason(s) for expressing and your personal preference. We all respond differently to pumps and have different needs.

Single electric pumps and manual pumps are best suited to occasional expressing, for example, short term separation or a return to work. They can also be used to express ‘to comfort’ any time your breast feels very full and your baby doesn’t want to feed.

Double electric pumps express milk from both breasts at once, which often saves time. It is also said that they tend to stimulate more milk production. They are available as personal use pumps and ‘hospital grade’ pumps.

Hospital grade pumps are very powerful and are intended to be used by more than one person multiple times a day. They are usually hired. Hospital grade pumps are recommended when you are exclusively expressing, expressing very frequently, or trying to increase your supply. Parents might start with a hospital grade and then switch to a personal use pump once their supply is established and if they need to keep expressing.

Silicone pumps tend to be best suited to occasional use. Some mothers have found them helpful to relieve blocked ducts. (Note: When attached to the breast, a silicone pump is not just a device for collecting dripping milk – it creates a vacuum stimulating a ‘letdown’. If this is not your planned use, it can create supply issues.)

Hands-free pumps come as single or double electric pumps. They can be handy for mums who want to pump on the go, or pump and multitask. Hands-free pumps have small motors and are possibly best suited to occasional pumping. You can buy or make a hands-free bra for a pump to fit in to.

line drawing of manual pump, single electric pump and double electric pump

Types of Pump (image above)

A. Manual breast pump
B. Single electric pump
C. Double electric pump

It is also possible to express without any equipment. Hand expressing is a great skill to learn for all ages and stages! It can take a little practice, but it can quickly become second nature:

It is free and can be done any time, anywhere!
It is the perfect choice for the early days when you are producing colostrum (you can collect – or ‘harvest’ – colostrum before your baby is born).
You can practise antenatally and become familiar with your breasts before your baby arrives.
Getting ‘hands-on’ during a pumping session can increase milk output. See Expressing Tips.

What else do I need to know about pumps?

Pump fit

Pumps are often sold in a standard size, however pump parts come in different sizes. The funnel-shaped piece that touches your breast is usually called a flange. The tubed-shaped bit that the nipple goes into is sometimes called the nipple tunnel.

If pumping is comfortable with good milk flow, you probably have a good fit. However, if pumping is painful or causing swelling and/or rubbing, you may need a bigger or smaller flange. Sometimes a different flange size is needed for each breast. A poor fit can also reduce milk flow.¹

The nipple should have enough room to slide in and out during pumping, without rubbing. The areola (darker area around the nipples) may move slightly with it, but it shouldn’t be drawn into the nipple tunnel. After pumping, the nipple will almost certainly be bigger, but shouldn’t seem darker or swollen.²

showing different pump flange sizes, which ones is too small, just right, and too big

Pump Flange Sizes (image above)

A. Milk expression
B. Flange is too big
C. Flange fits
D. Flange is too small

Suction strength and cycle speed

Electric pumps often come with a range of settings. There will be settings for suction strength and settings for cycle speed.

A pump is trying to mimic a breastfeeding baby. When a baby nurses, they do a fast, light suck to trigger a letdown. Once the milk lets down, the sucking slows and they swallow more.

You might begin by using a low suction, high speed setting and once your milk starts flowing, switching to a higher suction, lower speed setting.

Exactly how high or low depends on how it feels and if it is removing milk well. Expressing should be comfortable, and a pump provides most milk when it is set at the upper end of fully comfortable.³

Painful pumping may impact milk flow, damage your nipples, and is unlikely to make you feel like doing it!

How often and when should I express?

If your baby can’t breastfeed yet, aim to express 8–10 times in a 24-hour period, including at least once at night. These do not need to be at regular time intervals, but avoid stretches longer than 5 or 6 hours. Once your supply is well established, you may find that you can get by with fewer sessions.⁴
If you are trying to make more milk, express after or between feeds. How often depends on how much more milk your baby needs and how feeding at the breast is going.
If you are returning to paid work, how often you express will depend on a number of things. Some parents look at how often they feed on average in a 24-hour period and work out how many feeds they will typically have when they are with their child, so express the same number of times when separated to maintain this daily average.
If you are stockpiling milk for short-term separation or in the run up to a return to work, express once or twice a day after or between feeds. If your baby typically feeds from one breast, you could express from the other side while they feed. The amounts may seem small, but they quickly build up!
Some mothers try ‘power pumping’ as a short-term strategy to increase their milk supply, or when they are struggling to fit pumping into their daytime routine. This approach involves expressing very frequently for short periods, stopping and starting as many times as possible – it is said to mimic cluster feeding.

How long should I express for?

Just like breastfeeding, expressing milk is not a ‘one-size-fits-all’. Observe your milk flow, notice how your breasts feel and find what works for you.

If you are using a single pump, this usually takes about 20–30 minutes for both breasts. You might try switching sides when the milk flow slows, usually every 5–7 minutes.⁵
Double pumps save time. A double-pumping session that replaces what would have been nursing will probably last no more than 15 minutes. However, it is more important to pay attention to your breasts than the clock.⁶

How much milk will I express?

How much we can express at any one time depends on lots of different things. If you’ve never used a pump before, it might be helpful to think of the first pumping sessions as practice.⁷

Expect small amounts in the early days. This will be drops for some and as much as a teaspoon for others. Many parents think of it as ‘putting in their order’ for more milk later.⁸
If you are breastfeeding full-time, expect to express around 15–60ml (0.5–2 fl oz) in total from both breasts per pumping session.⁹
If you are exclusively pumping, consider the overall volume in 24 hours. Full milk production is about 750–900 ml (25–30 fl oz) per baby. Milk production reaches its peak at about five weeks and stays relatively stable until around six months.¹⁰
Once milk production peaks, a typical feed is about 60–120ml (2–4 fl oz).¹¹

We all respond differently to pumps. How much you can express is not always a reliable or accurate sign of how much milk is there. It’s important to remember that a baby who is nursing effectively will get more milk than a pump.

Expressing tips

Before expressing:

Wash your hands and get comfortable
Put something warm on your breasts, such as a warm flannel
Gently massage your breasts
Use any objects or techniques that help you to feel calm and relaxed. This might be a photo of your baby, an item of their clothing, a favourite warm drink or snack, music or visualisations.

While expressing:

Try ‘hands-on pumping’. This is said to produce better results than relying on a pump alone¹²
- Use breast compression to increase milk flow
- Take a break midway and gently massage the breasts to help increase the amount of milk.¹³
- Hand express from both breasts after you have finished pumping.

Try nursing your baby on one side and expressing on the other, or expressing from both sides at the same time, to encourage more letdowns

After expressing:

Hand-express for a minute or two to help increase output and supply.

Cleaning pump parts

There is not complete agreement about cleaning pumping equipment. Some public/advisory bodies (including NHS England) recommend sterilising equipment after every feed.
Others recommend washing pump parts thoroughly after every feed and sterilising once a day.
Some advisory bodies and breastfeeding organisations state that pump parts do not need to be sterilised, and that washing in hot soapy water is enough if your baby is healthy and full term.

Day-to-day milk handling

There is very little research on the day-to-day problems of milk handling, so guidelines often err on the side of caution.
Fresh human milk kills almost all bacteria, viruses and fungi that it comes in contact with.¹⁴
Mothers who are exclusively expressing, or expressing frequently, sometimes put the whole pumping kit (flanges attached) in a clean container in the fridge until the next expressing session and clean everything at the end of the day.
Breastmilk can be safely stored at room temperature for up to 4 hours (see below). Some parents apply the same timeframe to their pump and pump parts, and express multiple times within a 4 hour period before cleaning everything.
One quick method of sterilising is to use a sterilising fluid that you change every 24 hours. Submerge pump parts in the solution after washing them each time.¹⁵

Washing and drying

Ensure hands and pump area are clean.
You may like to use a separate basin and separate utensils for cleaning pump parts and equipment rather than the sink.
Clean with hot soapy water and rinse separately with clean water.
Some pump equipment is also dishwasher-safe.
Air dry or dry with paper towels.
Clean pump dials and switches with a disinfectant spray or wipe.
Store dry pump equipment in a clean container.

If you are expressing milk for a sick or premature baby, good hygiene is vital and sterilising is essential.

Storing Milk

How long can I store milk for?

There isn’t complete agreement about milk storage.
Wherever you are storing milk, the fresher it is, the better.
Good hygiene is important — clean hands, clean pump parts, clean storage.

For healthy, full term babies¹⁶:

Room temperature

Ideally, use within 4 hours.
Depending on room temperature and how clean storage conditions are, up to 6–8 hours may be safe.
Frozen milk that has thawed and kept at room temperature should be used within 4 hours.

Fridge

Ideally, use within 4 days.
When conditions are very clean, 5–8 days may be acceptable.
Store milk in the back of the fridge rather than in the door.
Frozen milk that has thawed in the fridge should be used within 24 hours.

Freezer

Ideally, use within 6 months.
Can be stored for up to 12 months.
Store at the back of the freezer, away from the door where temperatures may fluctuate.

Insulated bag

Use within 24 hours.

Milk left over after a feed should be used within 1–2 hours as it mixes with a baby’s saliva, although it may be safe to put it in a fridge for up to 4 hours.¹⁷

For premature or sick babies, consult with hospital staff and follow hospital guidelines.

Combining expressed milk

When combining milk expressed at different times, mix cold with cold:

Chill newly expressed milk before adding it to an existing container.
You can add refrigerated milk to frozen as long as there is less refrigerated milk than frozen.
Use within the time limit of the oldest expressed milk.

What can I store milk in?

You can store milk in any clean container, such as a hard (BPA-free) plastic or glass container with a tight-fitting lid, or a disposable milk storage bag.
Milk expands in the freezer, so leave space in the bag or bottle if you plan to freeze it.
Put the date on the container.

How much milk should I store?

Store milk in small quantities to avoid waste. Small amounts also defrost more quickly.
For babies older than one month, a feed is approximately 60–120ml. You could also store some smaller amounts in case you need to offer more.

How do I prepare stored milk?

You don’t have to warm milk – some babies like it cold!
If you do warm milk, run the container under a warm tap or place it in a pan of warm water.
Never use a microwave or heat milk directly.
Swirl milk to combine rather than shaking it.
If defrosting milk, thaw it overnight in a fridge or hold it under warm running water.
Thawed milk should not be kept at room temperature. It should either be fed immediately or put in the fridge.

Smelly milk

Sometimes milk smells or tastes soapy after a short time in the fridge or freezer. This is because of an enzyme (lipase) that breaks down fats in milk. The milk is completely safe and most babies will drink it. However, if they refuse to, heat freshly-expressed milk to scalding (bubbling around the edges, but not boiling) and then quickly cool and freeze it. Scalding reduces some of the immune factors, but may be the only option for some families. You can also experiment with the length of storage time needed for the milk to acquire the smell.

Feeding your baby your milk

See Further Reading and resources below for information on ways to feed your baby your expressed milk.

Written by Charlotte Allam, March 2023. Review due March 2026.

Photos courtesy of Lois Rowlands and Rae Vacher Lowe.

Online Information

Hand expressing:

Maximizing milk production when expressing:

Books

La Leche League International, The Womanly Art of Breastfeeding, Pinter and Martin, London: 2010.
Marasco, L & West, D Making More Milk, McGraw Hill, New York: 2019.
Mohrbacher, N., Breastfeeding Answers, Nancy Mohrbacher Solutions, Illinois: 2020.
Ruddle, L., Relactation: A Guide to Rebuilding Your Milk Supply, Praeclarus Press, Texas: 2020.