Big Boobs,Small Boobs and Breast Milk Supply  - Does Size Matter?

The joke used to be that I could get into a stag party wearing a bushman’s singlet and nobody would notice I was actually a girl. I was an A cup desperate to be bigger but, as a teenager influenced by media images of buxom , full busted women, the boob fairy seemed to have passed me by.Back then, I didn’t care about the function of breasts (aka breastfeeding). I just would have liked to have a ‘pair’.

Pregnancy made a few changes to my tiny boobs and when my baby was born, I woke one morning to pains that seemed as though they couldn't possibly belong to me – I had grown boobs overnight! Apart from the pain, I thought, if this is what breastfeeding does, count me in! I did know though, that breastfeeding was the healthy choice for my baby so I wasn’t only motivated by the promise of finally filling a bikini top (although it certainly felt like a bonus!).

Breastfeeding didn’t come so easily with that first baby – he fed at least every couple of hours day and night for months and when I was asked by the health nurse, ‘how many feeds a day? ‘ I must have looked confused. She then asked, “has he dropped any feeds?’ “Ummm. Maybe he’s gone from 24 to 20? “

Thankfully, this good woman had just returned from a stint in New Guinea where women didn’t watch clocks and babies were almost constantly attached to their mothers' breasts. My baby was happy and thriving so my nurse didn't question my milk supply.

Although everyone around me seemed to have their babies on strict feeding schedules and daily routines  – even bathing their babies daily before the 6am feed - it didn't make sense to me to stretch out a hungry baby so I pretty much fed him and loved him and he grew. Because the women around me were also formula feeding, I consoled myself that breastmilk digested more quickly than the cows milk based formula so it seemed natural that my baby would feed more often. My ignorance was blissful and my baby thrived.

For top tips to boost your breast milk supply, download our FREE ebook 'Making More Mummy Milk,Naturally' by Pinky McKay, IBCLC lactation consultant

Your breastmilk storage capacity - jugs or shot glasses?

We now know that women have different breastmilk storage capacities – a woman like me, with a smaller storage capacity, will need to feed her baby more frequently than a woman with a larger one.

Ultrasound studies by Dr Peter Hartmann and team at the University of Western Australia have shown that although healthy breastfeeding women produce similar amounts of milk over a twenty four hour period, breastmilk storage capacity can vary up to three times as much between individual women. However, this is not necessarily related to breast size and doesn’t influence milk production ability.  

Although some larger breasted women will have an abundant storage capacity, a smaller breasted woman may have a good supply of glandular tissue and less fat which will mean a better storage capacity, while another larger breasted woman may have more fat in her breasts and less glandular tissue and therefore have a smaller storage capacity despite having larger breasts.

Mums like Katie, who describes her breasts as changing from 'half a lime size' pre-baby to 'oranges' while breastfeeding, have a great supply and a good storage capacity despite smaller breasts ;   Coby, who has ‘rock melons’ (medium to large breasts) initially struggled with low supply but with medication now has a supply that she says is ‘just right’ for my four month old. Then there are mums like Vicki who has big breasts and a big supply that meets the needs of her twins.

What this means is that while some women who have a larger storage capacity will be able to feed their babies enough milk to go three or four hours between feeds (providing their baby has a big enough stomach – newborn stomachs are tiny), other women will need to feed their babies more often. For women with a smaller storage capacity, a three or four hourly feeding schedule could result in a hungry, unsettled baby and a mother who questions her ability to produce enough milk.

Instead of becoming stressed about how much milk your breasts are making or storing, I joke that we have either shot glasses or ‘jugs’ and to consider, you can drink a litre of water from a large mug or a smaller cup (or a schooner or a shot glass!) and if you are drinking from a smaller cup, you will simply need more refills. This means that if you breastfeed your baby according to his hunger signals, you will never need to worry about your milk storage capacity.

Supply and demand

Milk production works on a supply and demand basis, according to Dr Hartmann’s research , an empty breast will make milk more quickly than a full breast so milk production will speed up or slow down according to how hungry your baby is and how well he empties your breasts: If your baby doesn’t drain your breasts or you space out feeds to allow your breasts to ‘fill up’ your hormonal processes will signal your breasts to make less milk.

When size may matter

So you see, generally, size doesn’t matter. However, there are some medical conditions that can impact milk supply regardless of breast size and for a small number of women, size and shape can be an indicator that there could be challenges to milk supply.

For these women, there may be little or no breast development during puberty and a lack of breast changes during pregnancy or when their baby is born. And this can impact milk supply if they have a condition called Mammary Hyperplasia or Insufficient Glandular Tissue (IGT). A study by Kathleen Huggins and colleagues of 34 mums with breast hypoplasia concluded that other markers that mothers may have this condition include: widely spaced breasts (breasts are more than 1.5 inches apart); breast asymmetry (one breast is significantly larger than the other); the presence of stretch marks on the breasts, in absence of breast growth, either during puberty or in pregnancy and tubular breast shape ("empty sac" appearance).

According to lactation consultant, Diana Cassar-Uhl, “the unfortunate reality of hypoplasia is that, although it is often easy to recognize in hindsight, the first clue that a mother has insufficient glandular tissue is usually primary lactation failure; her body simply does not produce milk. Even when everything else is in place for a good start to breastfeeding, the milk does not "come in" or is not enough to sustain her baby.”

This can be devastating for a mother who wants desperately to breastfeed her baby but has to adjust her goals. And, although this is another complete topic in itself, with the right support and acknowledgement, many of these women will manage some level of breastfeeding.

Marina, a client of mine who has Mammary Hypoplasia contacted me during her second pregnancy after a disappointing experience with her first baby. Together, we made a breastfeeding plan which included lots of support, skin to skin resting with her baby as milk supply was established, donor milk screened and ready in case she needed to supplement, a nursing supplementer device (SNS) galactagogues (lactogenic foods and safe herbals) based on her medical history, and a postnatal visit scheduled to check on her feeding.   This time around, albeit with supplementary feeds  of donor milk as necessary, Marina continued to breastfeed until her daughter weaned as a toddler, despite the size of her breasts.

Listen to Pinky's Podcast interview with Marina, a GP as she discusses her breastfeeding journey with IGT and how this has influenced how Marina cares for mothers as a doctor. 


 Pinky McKay is Austalia's most recognised and respected breastfeeding expert. She's an IBCLC lactation consultant, best-selling baby care author and creator of Boobie Foods, all natural and organic cookies and foods to boost energy and nourish breastfeeding mothers. For simple strategies to boost your milk supply, download Pinky's FREE ebook 'Making More Mummy Milk,Naturally HERE.