Why you can't REALLY choose your shield size when pregnant

Why you can't REALLY choose your shield size when pregnant

If you’ve been deciding which breast pump is best for you, then you may have noticed that Pumpables gives mamas the option to choose a breast shield size when purchasing a Pumpables breast pump.

This makes sense for women who are already direct breastfeeding and/or pumping, because you can just go ahead and measure your nipple after a pumping session, work out which size you are and make your purchase. Note - even in this case, it can take a little trial and error! (To measure your nipple, start here at pumpables.co/measure).

If you’re like many mamas and you’re purchasing your breast pump while you’re pregnant, then it is a little trickier. Although you CAN measure your nipple while pregnant, your nipples will change after your baby’s arrival in ways that are impossible to predict. The size, shape and even ‘stretchiness’ of your nipple may change, and all of those changes will impact your shield size.

With this in mind, let’s work out what to do if you’re pregnant and trying to figure out which shield size to purchase.

Choosing your shield size is a new thing

Pumpables is actually the first company to give you some choice around shield size when purchasing your breast pump, and there are now a few other companies doing the same thing. For decades, breastshields have been sold with a standard size offered, with additional sizes available in limited options and often hard to source - like women’s bodies are ever ‘one size fits all’, right? We would never assume everyone has the same shoe size, and it’s unfortunate that so many women have had to endure pumping with the wrong shield size!

-> If you’re looking for additional sizes, check out our universal shields

The only downside to our decision to enable you to choose your shield size when you purchase your pump is that it can be confusing if you have no idea what size you are, particularly if you’re still pregnant and haven’t pumped before. 

How to measure your nipple and find out your size

Measuring your nipple is simple. Head to pumpables.co/measure and print out the nipple ruler. You want a snug fit around your nipples, and ideally you’ll measure a couple of minutes into a pumping session. Most women size themselves incorrectly, so always feel free to ask us for another opinion.

-> Here’s more information on how to measure your nipple

You really can’t know what your nipples will measure UNTIL you’re pumping

When you start to pump, your nipples are likely to change in ways that are impossible to predict, everyone’s nipples behave differently when they start to lactate and questions about breast shield sizes often land in our inbox.

So we put it out to our community - asking our Pumpables users if they found a difference between their nipple size before and after pregnancy.

82% of the women we asked said their nipples changed noticeably after they gave birth.


A couple of mamas also shared their individual stories with us, almost unanimously agreeing that you really will have to wait and see.

  • Most women’s nipples will increase in diameter a little once pumping, which is why we ask you to measure during a pumping session. It’s impossible to know how much your nipples will swell when pumping until you’re actually doing it.
  • Many women’s (not all, but the majority) will increase in size once they give birth and are lactating.
  • Your nipple elasticity will also change - meaning the tissue of your nipples adapts. They may stretch lengthwise and swell more than anticipated - this is totally normal, but will also impact your shield size and which shield option is best for you. 

Sound complicated? Keep in mind that your shield size may even keep changing throughout your breastfeeding journey! 

Your body changes in all kinds of unpredictable ways when pregnant, and this is just another of them. Imagine trying to guess how big your belly will be at 9 months, or what size toddler clothes your unborn child will be wearing at age 2. You can have an idea, but you just can’t do it with any kind of accuracy. 

It’s still worth measuring your nipples when pregnant

Even though you really can’t figure out your shield size when pregnant and be confident that it won’t change once you’re breastfeeding, it’s still worth having a go at measuring your nipples.

Give yourself a ballpark

Although your nipples will change once you give birth, your measurements during pregnancy are going to give you a ballpark estimate. You can use this measurement to estimate what your shield size is likely to end up being and help you research the shield options that will be available for you. For example, if you’re measuring smaller during pregnancy i.e. 15mm, then you know that you’re most likely going to end up needing smaller shield size options.

Get used to measuring your nipples without the stress of baby around!

We get emails daily from mamas who have given birth, started pumping, and discovered that the pain or poor milk output they are feeling is due to using the wrong shield size. To measure your nipples and find out your true shield size can seem fiddly - you need to print out the ruler, find your scissors, use the ruler, and then take some photos using the ruler to send to us if you’re wanting our opinion. This is not ideal to be doing with a newborn baby around! If you can get the ruler printed out when you’re still pregnant and practice assessing shield size then you’ll find it a lot less stressful repeating this when baby arrives!

You should always check your shield size again once you’ve given birth

When you start breastfeeding and/or pumping, then expect that you’ll need to check your shield size again and see if anything needs to be changed. It’s a good idea to keep doing this at regular intervals. 

If you can’t figure out your size, start with the 21mm

If it all feels too hard and you just can’t figure out what size you’ll be, we recommend you start with the 21mm size. This size will fit most women without too many problems. If you start with a 21mm, and then get in touch once you’re pumping, we can reassess your size then and figure out if a different solution is needed.  

Get the right breast pump - you can always find shields to fit

If the breast pump you want doesn’t come with shields in your recommended size, there are lots of different inserts and shield options around these days so you should be able to find something to fit. For example, if you’re buying our SuperGenie hospital grade breast pump, and choose the 21mm Liquid Kit to bundle with it at checkout, then you will only need to replace your Liquid Inserts if the 21mm turns out to be too large.

Focus on choosing the right breast pump and just be aware you may need to come back and improve your shield fit once you’re pumping. A breast pump is a much more significant cost outlay than shields, so it’s more important to choose the right breast pump and then figure out shield size / options from there. 

It can take a little trial and error to figure out your perfect shield size, but we’re here to help you get it right. If you’re not sure whether your shield is working for you - investigate further. A good shield fit is critical for pain-free pumping and good milk output, and you deserve a comfortable experience.

Back to blog

Are you worried about shield fit? Download the Pumpables measuring tool to ensure you're using the right size