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Breastmilk Supply: What matters more, SIZE or SHAPE?

How many of you answered size? This is one of the most common misconceptions I have seen in my private practice. Most women are under the impression that their breast size will dictate how much milk they make. This could not be further from the truth.

When it comes to milk production, SHAPE is more predictive. This is one of the reasons I strongly encourage all first-time moms to get a prenatal lactation consult. During the consult, once we have gone over and reviewed a detailed medical and obstetric history, I perform a prenatal breast exam. Here are a few things I look for with examining your breasts:

Fullness (Appearance)

If I were to divide your breasts into four quadrants through the nipple, would you have the same amount of breast tissue in each quadrant? If not, where are you missing tissue, and how much? Missing tissue of breast hypoplasia can change the shape of and spacing between your breasts. Which leads me to my next exam...

Shape and Spacing

Are your breasts shaped more like an orange, roundish and full, or are they more like zucchini long and bulbar? How much space do you have between your breasts? Can I fit the palm of my hand, meaning there is 3.5cm or more spacing between them? The more tubular and spaced out your breasts are, the more concerned I am about you having Insufficient Glandular Tissue (IGT). IGT is a lack of the mammary tissue necessary for milk production.

Breast Hypoplasia
Revised tuberous breast deformity classification (von Heimburg). Plast Reconstr Surg 2000;105(6):2269–2270).
  • Type 1 - Mild hypoplasia in the lower inner quadrant

  • Type 2 - Mild hypoplasia with tissue missing in the lower inner and outer quadrant

  • Type 3 - Moderate hypoplasia with tissue missing in the lower inner and outer quadrants

  • Type 4 - Severe hypoplasia with minimal tissue in all quadrants, minimal breast base

Revised tuberous breast deformity classification (von Heimburg). Plast Reconstr Surg 2000;105(6):2269–2270).

Needless to say, the more tubular or hypoplastic your breasts are, the more likely you are to have difficulty with milk production due to the lack of mammary (milk-making) tissue. The bigger the spacing between your breasts, the more likely you will have missing tissue in the medial (inner) quadrants. You are more like to suffer from primary lactation failure.

"...condition occurs when a mother’s body does not make an adequate amount of milk for her baby, even when everything else (including but not limited to: latch and positioning, breastfeeding frequency and exclusivity, mother and baby are kept together, baby’s oral anatomy is fine – no tongue tie, cleft palate) is in order." -


Contrary to what we may think, seldom are our breasts exactly identical. I like to say for most of us, our breasts are sisters, NOT twins. And in some cases, they are cousins and even distant cousins. However, the more asymmetry I notice on an exam, the more concerned I am about a potential low or insufficient supply in the smaller, more hypoplastic breast. But worry not, I have had women successfully exclusively breastfeed.


I know I said size doesn't matter. However, if there is a change in the size of the breasts, such as a reduction due to removal of tissue from a reduction, mastectomy, any other surgical procedures or trauma to the breast, or an increase in size due to an augmentation or breast implants, that result in a disruption in the ductal and nerve systems, ones ability to produce milk in the future may be negatively impacted.

Most women will experience an increase in breast cup size and sensitivity throughout the pregnancy, especially in the 1st and 2nd trimesters and postpartum, due to the increase in progesterone and prolactin. Though this is not an absolute, coupled with any of the other concerning signs above, an absence of breast change prenatally and or postnatally can be predictive of a lower/inadequate milk supply.

Take Away

GET A PRENATAL LACTATION CONSULT! There is nothing more heartbreaking for me as a lactation consultant than having a woman go through her entire pregnancy without anyone catching and alerting her of any red flags above.

Connect with a local IBCLC and discuss your concerns. And if you can't find someone locally, book a virtual consult with me. Though not all breastfeeding concerns are appropriate for Telehealth, prenatal consults definitely are. We won't be able to predict exactly how much milk you will make based on just the prenatal exam, BUT we can definitely collaboratively create a breastfeeding plan that allows us to maximize your supply and, most importantly, set expectations on what success may or may not look like.



Hi, thanks for stopping by!

I'm Rue Khosa aka The Boob Boss. I am a nurse practitioner and IBCLC whose passion is supporting new and expectant parents through pregnancy and beyond. I believe in and teach

    Thrive Parenting...

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