Breastfeeding is a remarkable journey, and understanding the stages of lactation can help you feel more confident as your body adapts to your baby’s needs. Each stage comes with its own changes, challenges, and milestones, from pregnancy through weaning.
Think of milk production like a little supply and demand system. The more milk that’s removed from your breasts, the more your body will make to keep up. And here’s something moms often don’t realize—each breast actually works on its own! So one breast might produce a bit more or less than the other, and that’s totally normal.
What is Lactation?
Lactation results when the mammary glands in the breasts of a mother provide milk for her infant.
‘A mammary gland is an exocrine gland in humans and other mammals that produces milk to feed young offspring. Mammals get their name from the Latin word mamma, “breast.” ‘ – wikipedia.org
The Four Stages of Lactation…
Stage 1: Mammogenesis
The very first stage of lactation is called Mammogenesis—this is simply the development of your breasts to get them ready for milk production. And it starts earlier than you might think! When you were still in your mother’s womb as a tiny embryo, your breast tissue was already forming. By around 12 weeks of pregnancy, the nipples, areolae, and tiny mammary buds (the beginnings of the milk ducts) were in place.
As you grow up, estrogen and other hormones during puberty continue this process, prompting the breasts to grow and develop duct tissue. Each menstrual cycle adds to this development, with estrogen and progesterone temporarily stimulating the breast tissue.
But your breasts are only fully prepared to produce milk once you become pregnant. During pregnancy, hormones like prolactin, placental lactogen, estrogen, progesterone, and ACTH complete the final changes in the breast, preparing the alveoli and ducts so you can make milk for your baby. Read more about the hormones responsible for lactation.
Physical Changes and What to Expect
- During puberty and pregnancy, it’s normal to notice tenderness, swelling, or changes in nipple and areola color.
- These changes are your body preparing for milk production, and most are temporary.
Hormones at Work
- Estrogen & Progesterone: Grow breast tissue and ducts.
- Pituitary growth factors: Help the glands mature.
- These changes are gradual and vary for every woman.
So, What Changes Occur During Pregnancy?
During pregnancy, your breasts go through some pretty amazing changes to get ready for feeding your baby. A whole network of milk ducts starts to spread and multiply, making sure milk can flow easily later on. You’ll also notice your areolae (the darker area around your nipples) becoming larger, and those little bumps on them—called Montgomery’s tubercles—will become more noticeable. Even your nipples themselves usually become more extended, all part of your body’s natural preparation for breastfeeding.
Stage 2 & 3: Lactogenesis
Inside your breasts, there’s a fascinating milk-making system at work. Each breast contains about 15–20 lobes of glandular tissue, and within each lobe are tiny clusters called alveoli—these are your milk-producing cells. You can picture them like little bunches of grapes. The milk made in the alveoli flows into small ducts (called ductules), then into larger ducts, and finally comes out through the nipple openings. Along with this, your breasts are filled with nerves (which trigger the let-down reflex) and lymph vessels that help keep the breast tissue healthy.
Now, let’s look at how milk-making (lactogenesis) unfolds:
- Stage 1 happens from mid-pregnancy until about two days after birth. At this point, the alveoli are already busy creating colostrum (that thick, yellow “liquid gold”), and your breasts may feel fuller or heavier.
- Stage 2 begins around day three to day eight postpartum. This is when milk “comes in.” The alveoli cells become more tightly packed, which increases production of lactose, glucose, and milk lipids while reducing the levels of protein, sodium, chloride, nitrogen, and magnesium. During this stage, many moms notice their breasts feeling warm, full, or even engorged if they’re not emptied often enough.
If milk isn’t removed regularly, your body starts a process called involution—this is where milk production slows down and eventually stops. But it’s important to know: your milk doesn’t turn back into colostrum. Instead, the supply just gradually decreases. If you start feeding or pumping again soon enough, your body can usually pick production back up.
Practical Tips for New Moms
- For engorged breasts, try frequent feeding, hand expression, or a warm compress to relieve discomfort.
- Gentle breast massage can help milk flow more easily.
Signs Your Milk Is Coming In
- Breasts feel fuller, warmer, or heavier around day 3–5 postpartum.
- Baby may feed more often—this is normal!
Hormones at Work
- Prolactin: Stimulates milk production.
- Oxytocin: Triggers let-down reflex for milk flow.
Normal vs. Concerning Signs
- Some engorgement is normal.
- Redness, extreme pain, fever, or hard lumps may need attention from a lactation consultant.
‘The processing and packaging of nutrients within human milk changes over time as the recipient infant matures. For example, early milk or colostrum has lower concentrations of fat than mature milk but higher concentrations of protein and minerals’ – emedicine – The stages of lactation
Stage 3: Galactopoiesis
Lactogenesis stage 3, also called Galactopoiesis, begins around day 9 postpartum and lasts until you and your baby decide to wean. This stage is all about maintaining your milk supply and keeping up with your baby’s needs.
At this point in the stages of lactation, milk production shifts from being mainly controlled by hormones to being managed by the autocrine system—which means your breasts now work on a supply and demand basis. The more often milk is removed, the more your body will make.
Each breast works independently, so if your baby nurses more from one side, that breast will naturally produce more milk than the other. That’s why some moms are able to successfully breastfeed from just one breast if needed.
Hormones like prolactin and oxytocin are still active in the background, helping with milk synthesis and let-down, but the main driver is now how much and how often milk is emptied from your breasts.
How to Keep Your Supply Steady
- Feed or pump frequently—milk production is mainly driven by supply and demand.
- Emptying each breast fully ensures it keeps producing milk efficiently.
Practical Tips
- Each breast works independently—if your baby prefers one side, it’s okay.
- Pumping or feeding from both sides occasionally helps balance supply.
Signs of Adequate Milk
- Baby’s wet/dirty diapers, weight gain, and alertness.
- Breasts feel softer after feeds.
Why Does the Breast Produce Less When It Feels Full?
Your breasts are really smart—they’re designed to make just the right amount of milk for your baby. When the breasts are very full, milk production naturally slows down. This happens for two reasons:
- Prolactin receptors (the little “doors” that prolactin uses to signal more milk production) can’t work as effectively when the alveoli are stretched and full.
- A special whey protein in breast milk, called the Feedback Inhibitor of Lactation (FIL), tells your body to slow things down when the alveoli are crowded with milk.
Once milk is removed and the alveoli aren’t as full, FIL levels drop, and prolactin can bind more easily again. This sends the message to your body to start making milk more quickly.
This is why frequent milk removal—whether through breastfeeding or pumping—is the key to keeping up a good milk supply.
Stage 4: Involution
Stage 4 of lactation is called Involution. This is the process your breasts go through when milk production gradually slows and eventually stops, usually after you wean your baby. During involution, the alveoli shrink and the milk-making cells are reabsorbed, returning the breast to its pre-pregnancy state over time.
Think of it as your body naturally winding down milk production once your baby no longer needs it—it’s a normal, healthy part of the breastfeeding journey.
Gradual Weaning Tips
- Slowly reduce feeds to avoid engorgement or discomfort.
- Express a little milk if needed to relieve pressure—don’t rush the process.
What’s Happening in the Body
- After weaning or when milk removal stops, the alveoli (milk-producing cells) shrink, and many undergo apoptosis (programmed cell death).
- The secretory tissue is largely broken down, and the breast gradually returns to a state similar to pre-pregnancy.
- Some alveoli and ducts remain, so the breast can regenerate milk-producing tissue in a future pregnancy.
Emotional Considerations
- Some moms feel emotional during weaning due to hormonal changes.
- This is normal—take it slow and listen to your body.
Resources
- Ncbi.nlm.nih.gov – Lactation
- Sciencedirect – Physiology of Lactation
- Medscape – Human milk and lactation
Understanding the stages of lactation helps you support your milk supply, recognize normal changes, and confidently navigate breastfeeding from start to finish.
