Feeding
Expressing and storing breast milk
Output from a pump is a poor measure of supply, and the storage guidance is specific for good reasons.
Expressing is one of the most misunderstood parts of feeding, mainly because the volume in the bottle is treated as a measurement of something it does not measure.
Why output is not supply
A baby is considerably more effective at removing milk than a pump.
Milk ejection depends on oxytocin release, which is triggered by the baby and is affected by stress, pain, distraction and being watched by a machine.
Which is why a mother producing plenty may express very little, and why a low pumping output is not evidence of low supply.
The reliable indicators of supply remain the baby's weight gain, nappies and behaviour.
Choosing a method
Hand expression is free, effective — particularly for colostrum, which is thick and small in volume — and worth learning from a midwife or a video regardless of what else you use.
Manual pumps are inexpensive and suit occasional use.
Single electric pumps suit regular use.
Double electric pumps save time and produce higher output and higher prolactin response, which matters for anyone expressing regularly.
Hospital-grade pumps are used where supply must be established without a feeding baby, as in neonatal unit admission, and can be hired.
Wearable pumps are convenient and generally less efficient.
Flange fit matters considerably and is the most common reason for pain and poor output — the standard size supplied frequently does not fit, and sizing should be based on nipple diameter.
Making expressing more effective
Practical points.
Be warm, comfortable and unhurried.
Look at the baby or a photograph, or express next to them.
Warmth on the breast beforehand and gentle massage help.
Use a lower suction than feels maximal, since higher is not better and causes damage.
Hands-on pumping — massaging and compressing while pumping — increases output measurably.
Express in the morning, when supply is generally highest.
And express after or between feeds if building a supply, rather than replacing feeds, since supply follows demand.
Storage guidance
Widely published and worth following precisely.
Freshly expressed milk can generally be kept at room temperature for a few hours, in a refrigerator at four degrees or below for several days, and in a freezer for several months, with the exact figures varying slightly between national guidelines.
Store at the back of the fridge or freezer rather than the door, where temperature fluctuates.
Use sterile containers or purpose-made bags, label with the date, and store in small quantities to avoid waste.
Milk separates on standing, which is normal — swirl rather than shake.
Colour varies with diet and is not a problem.
Thawing and warming
Thaw in the fridge, or under cool then warm running water.
Never use a microwave, which heats unevenly, creates hot spots and damages some components of the milk.
Warm by standing the container in warm water.
Use thawed milk within the period specified in your national guidance, and do not refreeze.
Milk left over after a feed should be discarded, since bacteria from the baby's mouth enter the bottle.
The lipase question
A common and confusing problem.
Some mothers find that stored milk develops a soapy or metallic smell, caused by lipase breaking down fats.
The milk is safe, and some babies refuse it.
Scalding the milk briefly before storing — heating until small bubbles form at the edge, then cooling rapidly — deactivates the enzyme, at a small cost to some milk components.
It is only worth doing if the baby actually refuses the stored milk, which many do not.
Returning to work
The most common reason for expressing regularly.
Building a modest freezer stash rather than a large one, since a few days' worth is generally enough and oversupply creates its own problems.
Expressing at roughly the times the baby would feed maintains supply.
Legal entitlements to breaks and facilities for expressing at work vary by country and are worth checking, since many people do not know what they are entitled to.
A cool bag with ice packs transports milk safely.
And babies frequently reverse-cycle, feeding more at night and less during the day, which is a normal adaptation.
Exclusive expressing
A demanding route that some families take by necessity or choice.
It requires expressing at the frequency a baby would feed, particularly in the early weeks and including at night, since prolactin is highest then.
It is legitimate, it is breastfeeding, and it is considerably more work than either direct feeding or formula.
Anyone doing it deserves support rather than a suggestion that they should be doing it differently.
General information only, not medical advice. Storage guidance varies by country — follow your national recommendations and consult a lactation professional about expressing.
