What is happening at six to twelve weeks

In the first weeks after birth, milk production is driven largely by hormones and is generous — often more generous than your baby needs. That is why the early weeks come with hard, heavy breasts, leaking, soaking through pads and dramatic let-down sensations. Over the following weeks, production shifts to being controlled mostly by how much milk is removed, and it settles at the level your baby actually takes. The surplus goes.

The American Academy of Pediatrics describes this change directly in its account of mature milk: breasts may appear somewhat softer and smaller than they did during the transitional-milk stage, and these changes are normal and designed to provide exactly what your baby needs. La Leche League GB's account of how milk production works gives the timings: production reaches close to peak by around ten days, and by about a month most people are making as much milk as their baby will ever need.

The list of things that disappear, and none of them mean less milk

Fullness between feeds. Breasts feel soft most of the time.
Leaking. Pads stop being necessary.
The tingling let-down sensation. Many people stop feeling it entirely; some never felt it at all.
Waking up engorged after a longer stretch of sleep.
Getting much when you pump. There is no longer a surplus sitting in the breast waiting to be taken.
Long feeds. Babies get much more efficient. A five-minute feed at three months can transfer what took twenty-five minutes at three weeks.

Every one of those changes is commonly misread as a supply failure, and the two that cause most panic — soft breasts and short feeds — are actually markers of a system working well.

How to check whether anything has really changed

The NHS and the HSE both point at the same evidence, and none of it involves how the breast feels:

Nappies. From about day five onwards, at least six heavy wet nappies in 24 hours, with pale, mild-smelling urine.
Weight gain over time. Plotted on a growth chart across weeks, not compared week to week. Babies often track along their own line rather than the middle one.
Behaviour. Alert periods, good muscle tone, and settling after most feeds.
Feeding activity. Deep, slow sucks with visible swallowing, rather than fluttering.

If those are fine, your supply is fine, however soft your breasts are.

When it is a genuine drop

The Australian Breastfeeding Association's list of real causes is a good checklist, and most of them come down to milk being removed less often:

Fewer feeds. Most young babies need 8 to 14 feeds or more in 24 hours. Stretching gaps, timing feeds by the clock, or limiting how long a baby feeds all reduce removal.
Formula top-ups or lots of solids. Every replaced feed is a signal to make less.
Heavy dummy use in place of offering the breast. Feeding cues get missed.
Hormonal changes. A brief dip around ovulation or a period is common; a longer decrease can come with pregnancy or with some types of contraception.
Illness or certain medicines. Being very unwell can lower supply temporarily.
A baby who is not feeding effectively, because of latch, tongue tie or illness.

Sudden versus gradual

Gradual softening across weeks is regulation. A sudden change over a day or two, especially with a baby who has become unsettled at the breast or whose nappies have changed, is worth a same-week conversation with your health visitor, public health nurse, GP or an IBCLC lactation consultant.

What to do if you want to lift it back

The lever is removal, not effort. Feed more often rather than for longer, offer both sides and then go back to the first, use breast compression to keep your baby actively swallowing, and reduce top-ups gradually rather than all at once. Skin-to-skin contact and a few days of doing very little else is crude but effective. What does not reliably work is teas, cookies and supplements; the evidence for herbal galactagogues is weak and none of them substitutes for taking milk out.

The reassurance most people are actually looking for

Being told that your breasts feeling empty is normal does not always land when you are frightened. So here it is as a test rather than a reassurance: a soft breast still makes milk while your baby feeds. Production is fastest when the breast is drained, not when it is full. If you put your baby on and watch for swallowing, you will see the milk arriving in real time. That is a better piece of evidence than anything you can feel between feeds.

Why the four-month mark trips people up

Around three to four months a lot of things arrive at once: soft breasts, very short feeds, a baby who pulls off to look at the room, more night waking, and often a return of periods. Individually each is normal. Together they read like a crisis, and this is one of the most common points at which people start topping up.

Before you change anything, check nappies and weight. If those are fine, the sensible move is to feed more responsively for a few days rather than to introduce a bottle — because a top-up removes a removal, and that is the one thing that genuinely reduces supply.

What to do about the worry itself

If you are checking your breasts repeatedly, weighing your baby weekly, or pumping to see what comes out, that pattern tends to increase anxiety rather than resolve it. Ask for one proper assessment — a feed watched start to finish and a weight plotted on a chart — and then give yourself permission to stop measuring.

My Breasts Feel Empty and Soft: Has My Supply Dropped?