One of the biggest fears I had before my son was born was about breastfeeding. What if it didn’t work? What if I never made any milk? What if my body just didn’t know how to do it? What helped the most (besides having a school friend working on her Lactation Consultant certification and always being available for questions), was understanding exactly HOW this “feed my baby with juices squeezed from my body” thing worked. Sure, milk come from breasts, but … HOW?
The following is a step-by-step look at how breastmilk is made and how it gets out of your body. Next time we’ll look at what’s going on with baby and their latch, but for now we’ll stick with the boob-side of things.
Step One: The Parts
The first thing to remember is that the size of your breasts has almost NOTHING to do with how much milk you can make. Milk comes from the mammary glands (the purple, grape-like circles in the diagram above), while the size of your breasts is based on how much fat is in them (the yellow stuff in the diagram). So the joke about Dolly Parton being able to feed an army because she is so well-endowed? Not really how it works.
So the milk is made in the mammary glands, and travels down through the milk ducts, little tubes that connect the glands to the nipple. Before the milk gets to the nipple, it hangs out in the milk sinuses, the little pockets behind the nipple — this stop will become important when we talk about the baby’s latch. The milk then exits the breast through holes (yes, multiple holes) in the nipple.
The other fun anatomy fact here is the areola, the skin that surrounds the nipple. You may have noticed it turning darker during pregnancy. After the baby is born, they see the contrast between light and dark colors very well; the dark nipple acts like a bullseye, guiding the baby to their food source.
Step Two: The Process
The mammary glands start getting ready during pregnancy (which is why your breasts may get tender or a little bigger than pre-pregnancy). The first milk that is made in the mammary glands is called colostrum — it’s thicker than “real” milk, yellow instead of white, and packs a different kind of nutrient and immunity punch for babies. The hormones in the placenta keep the mammary glands at bay until the baby is born. Once the placenta is gone, the hormone prolactin starts telling the mammary glands to get to work. Any colostrum already in the glands is sent down for baby’s first meal, and more and more colostrum will follow it for the first few days. After about three to five days, the colostrum will start to turn into “real” milk, which may arrive quickly and cause your breasts to get swollen and leak. This beginning process will happen whether or not your ever put baby to the breast — it’s automatic and totally based on hormones.
Step Three: Supply and Demand
After the initial, automatic process of making milk, the only way you can keep making milk is by removing milk from the breast — feeding the baby triggers your body to make more milk.
When the baby nurses, it sends a few different messages to the breasts and the brain. First, the baby stimulating the nipple releases oxytocin, which sends a message to the mammary glands to release the milk down through the milk ducts. Stimulating the nipple also sends a message to the brain that says, “Hey! There’s a baby stucking on our nipples! That baby might want to eat. Let’s make it some food!” The other major signal comes when the baby removes the milk from the breast. The empty breast sends a message to the brain that says, “Hey! This breast used to be full of milk, and now it’s empty. There must be a baby drinking it. Let’s make it some more food!” The brain then sends the hormone prolactin down to the mammary glands to get them to make more milk. The next time baby nurses, the whole process starts again — nipple stimulation and the newly empty breast tell the brain and the breasts to make more milk. If we interrupt this process and stop removing milk from the breast, the body will think there’s no baby to feed, and will stop making milk.
There are other hormones and chemical swimming around the body that can affect milk production — estrogen and progesterone from pregnancy, any stress hormones from birth, and anesthesia or pain medication. But the basic rules of milk production is of supply and demand — breastfeed that baby, and your body will make more milk.
Now that we have a solid understanding of HOW the milk is being made inside the breast, we can understand the changes in our own bodies and in our babies. If we run into issues with latch and milk supply, understanding the anatomy and physiology of a lactating breast will help us understand WHY we’re having trouble and HOW to fix it (we’ll talk more about that in another post). You can also just sit and marvel at how a group of glands — much like the salivary glands in your mouth or sweat glands under your arms — are all your baby needs in order to grow.