The amount of milk expressed right after the baby has breastfed is called the residual volume.
1) Residual volumes of 15 ml (1/2 oz) or less from each breast
Residual volumes of 15 ml (1/2 oz) or less from each breast happen if the mother:
- Has a full milk supply and the baby is getting enough milk from the breast.
- Does not express effectively.
- Has a temporarily reduced milk supply.
- Has a low milk supply.
If the baby has breastfed well, the residual volume is often 15 ml (1/2 oz) from each breast (Dewey 1991). The baby does not totally empty the breast.
Healthy mothers generally have a higher residual volume in the morning after a nighttime break and may find this is often a good time to express in order to store milk for later use.
Mothers with a low milk supply will wonder why the baby leaves milk behind in the breast yet needs to be supplemented. Consider two glasses of milk – one full and one half-full. After each glass is emptied, both glasses will have a little bit of milk in the bottom of the glass. Similarly, breastfeeding mothers will also have a little bit of milk left in their breasts, regardless of how much was there at the start of the feed.
Thorough emptying of the breast by expressing after breastfeeding can increase the amount of milk expressed if the breast can respond to this stimulation. However, not all breasts are able to do so.
2) Residual volumes of more than 15 ml (1/2 oz)
If a mother generally obtains significantly more than 15 ml (1/2 oz) of milk when she expresses after breastfeeding, the mother may:
- Have a full milk supply and the baby is getting enough milk from the breast.
- Have a large milk supply from the time of the baby’s birth.
- Have created a large milk supply by expressing.
- Be over-supplementing.
It is also possible that the baby may: