How milk is produced in breast: 5 important things every nursing mother should know

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To solve low milk supply issue, it is essential for you to understand how milk is produced in breast. By knowing how your ‘milk factory’ works, it is easier for you to pin-point what causes the supply problem, and address the issue more efficiently.

Many articles cite that milk production is all about demand and supply. As long as your breast receives a lot of ‘demand’, it will produce the required amount of milk. BUT, is that really true?

Sadly, NO.

Demand and supply process is just one part of milk-production stage and there are other factors that can affect your milk supply.

Are you ready to know more? Read further.

How breast grows

Prior to pregnancy, human breast is like a tree in a winter, with few branches and  few leaves. Only during pregnancy, the breast development reaches its maturity by developing glandular tissues and its necessary lactating cells.

It grows more branches (called ducts and ductules) and leaves (called alveoli) which contains milk-making cells (lactocytes). That’s why breasts tend to grow bigger and fuller during pregnancy.

When your baby is born, milk production starts at full speed. More milk-making cells are generated to respond to baby’s milk demand. This process typically occurs up to first few weeks postpartum.

As baby grows older, the milk demand slowly decreases, and breast responds by removing unnecessary lactocytes. Just like a tree in autumn in which the leaves start falling off the tree, the breast is slowly back to its pre-lactating stage.

The role of hormone in milk-making process

Milk production starts as a hormone-driven process during pregnancy and first few weeks after birth.

Prolactin, the major playing hormone, is at large quantity during pregnancy and reaches its peak at birth. But milk has not yet produced prior to birth because prolactin’s function was inhibited by progesterone presence. Instead, only colostrum was made at a small amount, and this is called lactogenesis 1.

Only after placenta is released after birth, progesterone level diminishes. Thus, the milk making process starts and quickly reaches its full speed, typically around 30-40 hours postpartum. This is when mother starts seeing ‘milk comes in’, whiter in color and more watery compared to colostrum. This full milk production is usually referred as lactogenesis 2 and requires more hormones: prolactin, insulin, and cortisol.

During the first few weeks after birth, prolactin level slowly decreases and finally reaches a steady lower plateau. At this stage, the prolactin receptors in breast multiplies. It is believed that the development of prolactin receptors in breast is largely influenced by frequency of suckling stimulation and milk removal in the early days. The more suckling and the more milk being removed, more receptors are developed. This receptor development is essential to sustain long-term milk supply.

As prolactin level reaches a steady state and its receptors being established, the milk production slowly evolved from hormone-driven to a demand-supply process whereby the amount of milk produced is regulated locally at breast.

These first few weeks are critical because this is the ‘calibration time’ whereby breast measures how much ‘machinery’ (milk-making cells with prolaction receptors) it needs to have to supply adequate milk. Thus, always ensure you have effective and adequately frequent milk removal (be it from baby’s suckling or by pumping).

Milk-ejection reflects (or also known as let-down reflects)

Baby suckles triggers release of oxytocine hormone that stimulates muscle-like cells to squeeze milk out of breast. This is called milk ejection reflects or let-down reflex. When this happens, the milk sprays out of breast. When you nurse your baby, you’ll notice he starts taking a big gulp in between suckling. Or if you ever pump, you would like have noticed this spraying effect.

If somehow, the release of oxytocine is hindered, be it due to stress or other psychological pressure, then let-down won’t happen, hence very little milk is removed from breast. As a result, your breast will think that it should cut down the milk production.

Now we know that having effective milk ejection reflect is essential, because it is what triggers milk removal from breast. No matter how much milk your breast has produced, if there’s no let-down, no milk will come out.

 

The demand and supply system

As mentioned at point no 2, breast milk production starts out as hormone-driven process, and settles down as a demand-supply system after a few weeks postpartum.

In this stage, a mother’s ability to produce milk depends on:

• Whether she receives enough and effective stimulation from baby suckling
• Whether she has good nerve system that is able to send message from breast to brain to produce more milk

In breast, there is a protein called FIL (feedback inhibitor of lactation) that increases linearly as the amount of milk increases. When breast is full, breast has lot of FIL, and hence it slows down further milk production. In opposite, the emptier the breast, less FIL is present and hence faster milk production.

This phenomenon leads to the golden rule of milk production:

• Empty breast: faster milk production
• Full breast: slow milk production

So do you think it is a good idea to wait until you feel your breast is full before nursing the baby?

The answer is no. The more frequent your baby nurse, the faster the milk production is. Don’t ever assume that soft breast means no milk.

Maximum breast milk storage capacity

How much breast milk can be produced and stored after feeding? This amount will differ for every mother. But you need to know that this storage capacity:

• Does not based on outer breast size, but based on amount of matured glandular tissue inside breast that develops during breast growth ( see point no 1)
• Will determine how often (the frequency) baby need to nurse

That’s why, some mothers can go up to 3-hour interval between feeding because she can store more milk, while some others need to nurse every hour because her breast has smaller  storage capacity. If you belong to the later group, always ensure that you nurse your baby frequently. This is important so that your baby gets enough milk and your breast is trained to produce milk in a high speed.

 

Now, let’s summarize what you have learnt just now.

1. Milk-making cells in breast grow and die depending on the breastfeeding cycles, starting from pregnancy, full speed at first few weeks post birth, and winding down as the baby weans.
2. The milk-making process starts out as hormone-driven process and settles down as a demand-supply process. Thus, the first few weeks after birth is critical time as breast is trying to calibrate how much ‘machinery’ it needs to have to produce plenty of milk
3. Effective and frequent milk removal (be it from direct suckling or pumping) is important in every milk production stage
4. Milk ejection reflex (let down) is essential as it serves as a gateway for milk flowing out of breast
5. The breast storage capacity differs among mothers, and that influences the frequency of breastfeeding

Grouping these points into several major factors, we can summarize these things into the above diagram, whereby: sufficient glandular tissue (A) covers 1 and 5, adequate hormone and receptors (B) covers 2, and efficient milk removal (C) covers 3 and 4.

By knowing these important points in how milk is produced in breast, it is easier to solve low milk supply issue. We can start identifying the cause by checking each of these factors, narrowing it down to the real cause and solve it more efficiently.

I hope this article helps you to better understand how milk is being produced in breast. Now tell me, among all of them, what do you think is the most critical factor in YOUR milk production?

More Resources:

1. Kellymom website
2. Making more milk by Diana West
3. Breastfeeding Basics
4. Nursing Nurture
5. Mobi Motherhood
6. La Leche League International

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