How many bra sizes do you go up when breastfeeding?

Many women find that their breasts grow larger when they are breastfeeding. This is due to increased levels of the hormones prolactin and oxytocin, which stimulate milk production. But just how much bigger do breasts get during breastfeeding? And how many bra sizes do women typically go up?

Quick Answer

Most women go up 1-2 bra sizes when breastfeeding. However, it varies quite a bit between individuals. Some women only go up a half size, while others may go up 3 or more sizes.

How Breast Size Changes During Breastfeeding

When a woman starts producing breastmilk, the milk ducts and alveoli (milk producing glands) become engorged and enlarged. This causes swelling and enlargement of the breasts. The amount of enlargement varies between individuals. Factors like genetics, breast shape and density impact how much growth is seen.

The most rapid breast growth occurs in the first few weeks of breastfeeding. Once milk supply is established, breasts may grow a bit more but the most drastic changes taper off.

It’s difficult to predict exactly how large breasts will get during breastfeeding. In one study, researchers found:

  • About 15% of women’s breasts enlarged only 1 cup size or less
  • 35% of women went up between 1 to 2 cup sizes
  • 35% increased between 2 to 3 cup sizes
  • 15% increased 3 or more cup sizes

As you can see there’s quite a bit of variability. The average amount of growth falls between 1-2 cup sizes. But some women only change a little while others grow a lot.

How Long Breast Size Increase Lasts

For most women, the fullness in breasts lasts between 3-6 months after giving birth. However, there is a wide range:

  • Some women start dropping back down in cup size after just 6-8 weeks.
  • For many it takes about 3 months for breast size to stabilize.
  • Some retain larger breasts for the entire duration of breastfeeding (6 months or longer).

If breastfeeding is discontinued, milk production slows and the breasts will start to return to their pre-pregnancy size. But after multiple pregnancies, some women find their baseline breast size is larger than before kids.

Why Estimate Bra Size Changes?

Predicting how many bra sizes you’ll go up can be helpful for a few reasons:

  • Buying new bras – Getting properly fitted nursing/maternity bras helps support enlarged breasts.
  • Preparing for changes – Some women are surprised by how much their breasts grow and change shape.
  • Postpartum clothing – Dressing for fluctuating breast size can be challenging after giving birth.

However, it’s impossible to predict exactly how your breasts will change. Be prepared to accommodate some fluctuation in bra size, especially in the early months of breastfeeding.

Factors That Impact Breast Size Changes

Not every woman experiences the same degree of breast enlargement with breastfeeding. Some factors that influence individual response include:


Younger women’s breast tissue tends to be denser. Denser breasts often experience more growth from breastfeeding. After late 30s, breast tissue starts to naturally get more fatty and may not grow as robustly.

Breast Size Before Pregnancy

Those with smaller busts before pregnancy seem more likely to stay closer to their pre-baby bra size. Women with naturally large breasts may experience more drastic fluctuations.

Number of Prior Pregnancies

Breasts often undergo permanent changes after each pregnancy/breastfeeding cycle. Second and third timers may not see as much change as first time moms.

Are Breasts Asymmetrical?

It’s common for one breast to produce more milk and grow larger. Women with asymmetry may experience more of a size difference.


Your family history gives clues to how your breasts may change postpartum. Moms and sisters often have similar breastfeeding experience.

Signs Your Breasts Are Growing

Some signs that breast size is increasing during early breastfeeding include:

  • Bra feels tighter even on loosest hooks
  • Spillage over the top or sides of bra cups
  • Indentations from bra straps or underwire
  • Leaking milk from inadequate breast containment

Breast fullness, tenderness, and increased vein visibility are also common indicators of enlarging busts.

Cup Size Vs. Band Size

Both the cup size and band size may shift post-delivery but don’t always change uniformly. Here’s how breastfeeding impacts band and cup measurements:

Band size

The ribcage expands during pregnancy and often doesn’t return to pre-baby size right away. So even if cup volume remains stable, many women need a larger band size after giving birth.

Cup size

Milk production is the big influence on cup size changes. Cup sizes reflect the volume of breast tissue. Increase in cup size is due to hormonally-induced breast swelling and enlargement.

For some women, the band size gets bigger but cup size may not change much. Other women may stay the same band size but cups grow. Many women go up in both band and cup simultaneousl

Breast Changes Beyond Size

There are many other changes that occur to breasts during breastfeeding beyond just size increases:

  • Increased fullness and firmness
  • Milk leakage and engorgement
  • Visible veins just under the skin
  • Darkening of the areola
  • Sore and sensitive nipples

Being aware of normal breast changes helps new moms understand what to expect and know when to ask for help. Most moms find that breast sensitivity and engorgement improve after the early weeks once milk supply regulates.

Ways to Accommodate Expanding Breasts

To adapt to the breast growth of early breastfeeding:

Invest in soft, supportive nursing bras

  • Schedule fittings at 6 weeks, 3 months and 6 months postpartum.
  • Opt for bras without underwire to avoid plugged ducts.
  • Look for wide straps that don’t dig in as breasts enlarge.
  • Choose styles with room for fluctuating breast size.

Wear stretchy tops and dresses

  • Tops with ruching or flexible fabrics adapt well.
  • Wear v-neck, wrap, tank or button down styles.
  • Size up in shirts, dresses and swim tops.
  • Camisoles layered under blazers or cardigans provides flexibility.

Consider breast pads

  • Disposable or reusable pads prevent embarrassing leaks.
  • Contoured and shaped pads look discreet under clothes.
  • Pads also help sensitized nipples.

Massage engorged breasts

  • Gentle massage under a warm shower can provide relief if breasts become overly full.
  • Avoid compressing breasts too intensely when engorged.
  • Cold compresses can also help ease discomfort temporarily.

When to Seek Help for Breast Changes

Consult a lactation consultant or doctor if:

  • Breast size seems exceptionally large or one breast is notably bigger
  • Signs of blocked duct or mastitis like soreness, hardness, heat and redness
  • Extreme pain persists despite massage and cold compresses
  • Concerns about milk supply adequacy

Most women find their breast size stabilizes around 3 months postpartum once milk supply is well established. But breasts continue changing throughout the breastfeeding journey. Tracking your bra size changes helps determine when it’s time to go shopping for new bras!

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