How breastmilk production works
by Cordelia Uys, NCT Breastfeeding Counsellor
February 2020
What does a lactating breast look like?
There are several ducts on the inside of a mother’s nipple which branch out into the breast; at the end of the ducts are alveoli containing milk producing cells. The cells take nutrients from the mother’s blood and turn them into milk. The milk ducts then transport milk to the tip of the nipple, where milk is released from several holes.
Oxytocin and prolactin:
The two main hormones involved in milk production are oxytocin and prolactin. Oxytocin, often called the hormone of love, causes the contractions of orgasm, birth and lactation. It promotes feelings of love, bonding and well-being, and increases trust and empathy. Prolactin is the hormone that creates milk; it too helps with bonding.
When a baby nuzzles round her breasts (or sometimes just when she’s thinking about her baby), a mother’s brain releases oxytocin, which travels in her blood down to her breasts, where it makes the muscles surrounding the milk producing cells contract and push the milk out. The removal of milk from her breasts then tells her body to make more prolactin.
Lactogenesis I and II:
Pregnant women produce colostrum from half-way through their pregnancy. It’s the birth of her baby and the delivery of the placenta that tells a mother’s body to start making transition milk. All pregnant women and new mothers will produce colostrum, and then early transition milk, whether they put their baby to the breast or not, as these stages (lactogenesis I and II) are both hormonally driven.
Lactogenesis III and supply and demand:
Once a mother’s milk ‘comes in’ on around day 3 or 4, milk production is driven by supply and demand. The vast majority of mothers can make all the milk their baby, or babies, need: it’s effective and regular removal of milk from her breasts that tells a mother’s body to start making mature milk. This stage of established lactation is called lactogenesis III.
In order for a mother’s milk production to be established and maintained in the early months, milk needs to be removed from both breasts at least 8 times in 24 hours. UNICEF talk about an average of 10 to 14 feeds a day, and many babies will feed more often than this. If you count how often you have a drink, as well as eating food, you’ll probably find it’s at least 8 times in 24 hours, even though, unlike your baby, you aren’t trying to double your weight in about 4 months.
The Feedback Inhibitor of Lactation (FIL):
Whenever breasts get hard and full, a negative feedback mechanism (known as FIL, or the Feedback Inhibitor of Lactation) kicks in, telling them to stop making milk. This means milk production slows down when breasts are full and speeds up when breasts are emptier. The more often a mother feeds her baby, the more milk she will make.
Cluster feeding:
Research has shown that women tend to produce more milk in the mornings, and that milk volumes gradually decrease as the day goes on. It’s therefore typical for babies to go longer periods between feeds at the start of the day, and then to feed much more often as the day goes on. This ‘cluster feeding’ is possibly an evolutionary development to ensure that there is a period of several hours each day when babies nurse very frequently, thus stimulating a good milk supply.
Babies also cluster feed when they’re going through a growth spurt.
Milk storage capacity and the importance of responsive feeding:
Women vary in the volumes of milk they produce. Some women have a much more generous milk supply than others. This isn’t always a good thing: oversupply can be quite challenging. On top of this women vary enormously in how much milk their breasts can store before the Feedback Inhibitor of Lactation kicks in.
From around one month, a breastfed baby will drink roughly between 60ml to 120ml per feed. If a mother can ‘only’ store 50ml in each breast, her baby will probably take both breasts at each feed and want to breastfeed relatively frequently. As long as this mother feeds her baby responsively, her baby will be able to gain weight nicely. However, if she only offers one breast per feed, or tries to space feeds, this risks under stimulating her breastmilk production.
If a mother can store 150ml in each breast, her baby will usually only want one breast per feed and will naturally go longer between feeds.
A mother’s milk storage capacity doesn’t matter as long as she feeds her baby responsively, as recommended by UNICEF. Responsive feeding is not only vital for establishing and maintaining a good milk supply, it’s also much kinder to babies. Adults don’t like feeling hungry or thirsty; imagine how much harder this is for a baby who has no concept of time.
The importance of frequent and effective milk removal:
In addition to impacting milk supply, if a baby isn’t feeding regularly enough or isn’t removing milk efficiently, (for example due to a poor latch or a tongue tie), mothers can develop one, or more, blocked ducts. If the blockage isn’t cleared quickly, either by breastfeeding or by pumping, milk can seep into the surrounding tissues, causing an inflammatory reaction, which is known as mastitis.
Links:
https://kellymom.com/hot-topics/milkproduction/
https://kellymom.com/bf/pumpingmoms/pumping/milkcalc/
https://www.nhs.uk/conditions/pregnancy-and-baby/breast-pain-and-breastfeeding/#blocked
https://kellymom.com/bf/concerns/mother/mastitis/