A mother’s milk supply usually adjusts to her baby’s needs after about 4 weeks of breastfeeding. Some mothers continue to make more milk than the baby requires, and this is known as ‘oversupply’.

Oversupply can make breastfeeding difficult for both mother and baby.

What are the causes of oversupply?

Breastmilk oversupply that continues after the first 4 weeks or so can have many causes. Feeding patterns may cause the oversupply, such as:

• feeding the baby on a set schedule rather than according to need
• pumping too much before a feed to make the breast soft and easier for the baby to latch onto
• the baby preferring to feed mainly from 1 breast

Other causes of oversupply include:

• an excess of the milk production-stimulating hormone prolactin in your blood (hyperprolactinemia)
• a congenital predisposition

How breastmilk oversupply affects your baby

Your baby may be unsettled or distressed during and after feeding, and it can be hard to know whether they are still hungry or are getting too much milk too fast. Your baby may:

• choke and splutter at the breast due to the high rate of milk flow
• have trouble latching onto the breast
• feed for only short periods of time leading to ‘lactose overload’
• have a lot of urine (more than 10 wees a day) or diarrhoea with green, frothy poos and nappy rash
• have excessive wind, causing unsettled, colicky behaviour
• bring up a lot of milk after breastfeeding
• put on weight quickly

How breastmilk oversupply affects you

Oversupply can also cause problems for you.

You might feel your breasts refill very quickly after feeding your baby. They might feel lumpy and tight after breastfeeding. You might also leak more than usual or have an explosive milk-ejection reflex, which makes it difficult to feed in public, and can cause difficulties for your baby at the beginning of feeding.

You could develop blocked milk ducts or mastitis and breast abscesses.

Oversupply can make breastfeeding a less pleasurable experience for you or your baby. Some mothers think about early weaning if oversupply is not diagnosed and managed well.

How is breastmilk oversupply diagnosed?

It is essential to have a health professional such as a lactation consultant, breastfeeding counsellor, doctor or child health nurse watch your baby breastfeed to diagnose true oversupply. It can easily be confused with breast engorgement or a fast ‘let-down’ reflex.

For help with the diagnosis and treatment of oversupply, contact a health professional, such as a lactation consultant, breastfeeding counsellor, or child health nurse, or call Pregnancy Birth and Baby on 1800 882 436.

How is breastmilk oversupply treated?

The aim of treatment is to reduce your milk production. This is best done while you are being supported by a lactation consultant, breastfeeding counsellor, or child health nurse.

‘Block feeding’ is a method that can help reduce milk supply in just a few days:

• Choose a time frame, usually from 3 to 4 hours, and feed your baby from only 1 breast during that time.
• Then change to the other breast for the same time period.
• Continue this pattern for a few days.
• You might need to hand express a small amount from the unused breast to relieve pressure or discomfort, but don’t empty it — the residual milk in the unused breast triggers the reduction in milk production.

Block feeding ensures that 1 breast always contains residual milk. This will trigger both breasts to reduce milk production, and should gradually resolve oversupply of milk. How long it takes depends on your situation.

Block feeding will also help to reduce the amount of thinner foremilk consumed by your baby. As your baby gets to drink more of the creamy hindmilk, you’ll see your baby’s stools get thicker. This tells you that you are on the way.

If your milk supply does not respond to block feeding, talk to your doctor.

The Australian Breastfeeding Association website has more tips about managing oversupply.