Does Your Breast Pump Flange Fit Well? (Rethinking How to Size Flanges for Best Fit)

This post may contain affiliate links (see full disclosure). As an Amazon Associate, I earn from qualifying purchases.

In this post, we’ll go over what can happen if you use the wrong breast shield size and how to figure out which size shield you should be using.

Did you know that the amount of milk you pump can be dramatically affected by whether or not you’re using the correct breast shield size? And did you know that the breast shield that came with your pump is likely the wrong size for you? Let’s talk about it.

(Breast shields are also sometimes referred to as “flanges”–I’ll be using both terms interchangeably. Note that we are NOT talking about nipple shields, which are something totally different!)

Boost Your Milk Supply & Keep It Up

Our FREE guide will give you 5 simple, proven tips to boost your milk supply and increase your pump output. Get results in as little as just a couple days!

Finding the right breast shield size (flange size) to maximize pump output

If you’re pumping–whether as an exclusive pumper, a parent going back to work, or someone who only pumps on occasion–it’s important to use the correct flange size for several reasons:

Using the wrong flange size can be painful.

A breast shield that is too small can cause painful abrasions on the nipple, while a breast shield that is too big can cause discomfort by pulling too much of the areola (the darker skin around the nipple) into the flange, resulting in swelling. Pumping shouldn’t be painful!

Using the wrong flange size can lower pump output.

Have you ever noticed that your breasts don’t typically leak? Well, let me clarify: If your breasts are very full they might leak, but generally speaking, milk only really flows when you have a let down. That’s because nipple/breast stimulation (via a nursing baby or a pump) sends a hormonal signal to the brain that causes the breasts to release milk.

Nursing parent and baby. Image shows hormones that trigger a milk letdown.
The Milk Ejection Reflex

If your pump does not stimulate your nipples/breast sufficiently, the signal your brain gets to release milk is going to be affected. Many parents using the wrong breast shield size notice that they are able to pump more milk (sometimes a lot more!) when flanges fit better.

Using the wrong flange size can lower milk supply over time!

In order to maintain milk supply, it is important to drain your breasts thoroughly.

Note: I use the word “drain” instead of “empty” because the breasts are never truly empty, since the very act of releasing milk causes the body to begin producing more. “Drained” breasts are those that have released as much milk as possible in a given nursing or pumping session.

You can think of it like this: The body keeps track of how much milk is removed from the breasts in a given day, and it uses this information to know how much milk to produce the next day. If your pump isn’t draining your breasts thoroughly, you’ll remove less milk from the breast than you otherwise should have. Your body will detect this change and adjust milk production down accordingly, usually over a (sometimes short) period of time.

If breasts are drained too infrequently or not thoroughly enough, milk supply will decrease.

Please note that in order to maintain milk supply, it is also important to pump often enough. You can learn more about what that means here.

Now that we know why using the wrong shield size can be problematic, let’s talk about how to figure out what your correct size is.

How to Choose The Right Breast Pump Shield Size

Most breast pumps come with a flange that is a standard 24mm in diameter. But not everyone has the same size nipples! And since the human body isn’t perfectly symmetrical, sometimes each nipple is a different size. So we have some measuring/evaluating to do.

Step 1: Check your pump manufacturer’s guidelines

Different pump manufacturers have different guidelines to determine shield size based on the different size shields they offer. Usually you will be asked to measure your nipple diameter. This means measuring the diameter of the base of your nipple (see the small pink arrow on the image below), not including any of the areola (the darker skin around the nipple).

measure nipple diameter at the base of the nipple, not the areola.

Once you have this number, consult your pump manufacturer’s guidelines to see what size shield they recommend. For example, according to Medela’s guide, a nipple with a diameter of 16 mm would use their 21 mm breast shield. Spectra recommends adding 2-3 mm to your nipple diameter to determine flange size. And so on.

This may not be the size shield you wind up using, but it’s a good starting point!

Step 2: Turn on the pump

It’s important to see how the nipple moves in the shield when the pump is on, so before you evaluate shield fit, place the shield on your breast and turn your pump on. It’s not unusual for the nipple to swell when pumping, so pump for a couple minutes before evaluating flange fit in order to allow any nipple size changes to take place.

Step 3: Evaluate fit

There are two different schools of thought when it comes to what good pump flange fit looks like. We’ll go over both.

Method #1

According to the first school of thought, your breast shield should fit such that your nipple can move freely in the tunnel of the flange without touching the walls of the tunnel. At the same time, you don’t want the nipple to have so much room in the flange that too much of the areola is pulled into it (see graphic below).

breast shield sizing

This is the guideline most lactation consultants are taught to follow, and it works for many parents. If you find this works for you–you’re comfortable and your pump output is appropriate (see this post for what that means)–you are all set!

parent with a good size breast shield for her nipple
This shield looks like it may be a good fit for this parent.

Method #2

If you suspect your pump isn’t removing milk from you effectively (i.e. draining the breast takes more than 15-20 minutes), or if you find pumping uncomfortable despite using the “correct” shield size (according to method #1 above), you may benefit from a newer way of thinking about flange fit.

Some lactation consultants have found that–at least for some parents–the best fitting pump flange is one that sits as close to the nipple as possible. This means that when pumping, only the nipple is pulled into the tunnel of the flange, and the sides of the nipple touch the walls of the flange. The nipple is able to glide gently back and forth in the tunnel without causing pain or discomfort: It should feel like a gentle tug or perhaps like nothing at all.

breast shield sizing

Huh? Isn’t that a contradiction?

At first glance, these two methods of evaluating flange fit might seem to contradict each other. But they actually don’t!

In method #1, the flange size that is “too small” is SO small that the nipple cannot move freely back and forth in the tunnel without causing discomfort. Rather than correcting this by adding a small amount of space between the nipple and the tunnel (method #1), method #2 solves this problem by making sure that the nipple can freely and comfortably glide back and forth inside the tunnel while still touching the sides of the tunnel.

What if I can’t get a good fit?

Fortunately, there are several options for pumping parents struggling to get a good flange fit.

If you have very small or very large nipples…

  • Check to see what flange sizes your pump manufacturer offers. Larger or smaller sizes may need to be ordered separately.
  • To make your flange smaller, you can try using a flange insert. Maymom flange inserts, for example, can reduce the tunnel diameter down as low as 10 mm!
  • If you need to make your flange only a bit smaller, using a breast pump cushion, such as the BeauGen cushions, may help.
  • Some shield brands work for a range of nipple sizes. For example, the Pumpin Pals small set covers sizes 15-25 mm and their large set covers sizes 24-40mm.
This breast shield is way too big for this parent
This flange is WAY too big for this parent no matter which flange sizing method you use! Notice how much space exists between the nipple and the flange tunnel wall. A smaller shield is needed.

If you have elastic nipples…

It is easiest to determine your correct flange size using a hard plastic flange. But for some people, a hard plastic flange isn’t ideal. If you have very stretchy nipples that get pulled far back into your flange tunnel (and may even touch the far end), you might have “elastic nipples” and may benefit from a silicone breast shield such as Pumpin Pals or a silicone breast cushion, such as the BeauGen cushions.

Elastic nipples

Do you need more help?

If you’ve adjusted your breast shield size and are still having trouble, I encourage you to meet with a qualified lactation consultant/IBCLC as soon as possible! You can learn more about how to find a qualified lactation care here.

If you’ve adjusted your breast shield size but are still struggling with low pump output or discomfort, a few things could be going on. Make sure you have realistic expectations about pump output (you can learn more about what normal pump output looks like here), and consider your pump settings. A pump that is using too much suction or pumping at a rate that is too fast might cause lower milk output or nipple discomfort even if you’re using the right size shield.

Be sure to bring your concerns to a qualified lactation consultant as soon as you can in order to prevent worsening supply issues!

Boost Your Milk Supply & Keep It Up

Our FREE guide will give you 5 simple, proven tips to boost your milk supply and increase your pump output. Get results in as little as just a couple days!

If you enjoyed this post, be sure to check out our digital library of helpful resources that quickly teach how to avoid common breastfeeding problems and give you the peace of mind and confidence you need to meet your breastfeeding goals.

You Might Also Enjoy:

Similar Posts