Jugs or Shot Glasses? Does Breast Size Impact Milk Supply?

 Have you heard that your breast size could mean you will make more or less breastmilk?

Are you anxious that having smaller breasts might create issues with milk supply, especially if your baby seems to be feeding pretty frequently?

Your breastmilk storage capacity – jugs or shot glasses?

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

Ultrasound studies by Professor 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. This can impact milk supply if they have a condition called Mammary Hypoplasia 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/ 4 centimetres 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 and lack of support 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 postnatal visits 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, (Marina is a GP/family doctor) as she discusses her breastfeeding journey with IGT and how this has influenced how Marina cares for mothers as a doctor.

Pinky McKay is one of Australia’s most recognised and respected breastfeeding experts. She’s an International Board Certified Lactation Consultant (IBCLC), mum of five  and best-selling author of Sleeping Like a Baby, Parenting By Heart and 100 Ways to Calm the Crying (Penguin Random House). See Pinky’s Books HERE (they are also available on Audible)