Lansinoh Moms' Club

Breast pump flange fit: Sizing guidance

image of person holding ComfortFit flange and touching rim

So you have a breast pump and are on your way to expressing milk for your little one. Maybe you’ve already even done some research to get ready—congrats! Next you may want to consider flange fit.

Say what? The flange is the funnel-shaped piece of the pump that goes around your breast. And different breasts may need different flange sizes.

Here’s what you should know about finding the right fit.

Why size matters

As you’ve probably figured out, breast pumps remove milk from your breasts using suction. The flange’s job is to form a comfortable seal around the breast, creating a vacuum. Then the suction action gently pulls the nipple into the tunnel on the other end, to get the milk flowing.

A flange that’s too big or too small can actually block your milk ducts, reducing the amount of milk you can pump. The wrong flange fit also can lead to engorgement, clogged ducts, milk blisters, and a decrease in your milk supply. Not to mention, it can be pretty painful!

You want pumping to be both comfortable AND worth your while. The right flange can make all the difference.

You’ve got options

Women’s bodies and breasts are all different, so it makes sense that flanges come in different sizes too. But choosing the right flange size is less about your bra size and more about making sure it allows your nipple to move the way it should.

Basically, larger nipples call for larger flanges. But there are other things to consider, too: our nipples might not be symmetrical, or they may respond differently to suction. Some women have very dense breast tissue while others have tissue that’s more stretchy and elastic. Nipple sizes also vary with ethnicity and age, and they tend to grow during pregnancy and breastfeeding. It may take a little experimentation to find the best fit for you.

Choosing the flange that’s right for you

So how do you know if you have the right fit? Start with the flange or flanges that came with your pump. If you haven’t had your baby yet, go ahead: Hold the flange up to your chest, center it on each of your nipples, and see! If the nipple fits comfortably in the flange, this is a good fit to get started. If the nipple touches the sides of the tunnel, you’ll want to try the next size up, and if there’s a lot of space around the nipple, you’ll want to size down. Just be patient and wait until baby arrives to try pumping out for real. Pumping during pregnancy may send you in to labor before baby’s ready to make their arrival.

Once baby comes and you start pumping, let comfort be your guide. You know you’ve found the right flange when:

      • The flange fits comfortably around the contours of your breast without digging into the flesh. (Using a flange with a soft, flexible rim can make pumping even more comfortable.)
      • Only your nipple and some of your areola enters the tunnel during pumping.
      • Your nipple moves freely within the tunnel during pumping, without rubbing.
      • Your breasts feel soft and lighter after pumping.
      • Your milk supply improves or holds steady. 

If your flange is too small
, the nipple will rub or be pinched along the sides of the tunnel. Pumping may take a long time, and your breasts may not feel empty afterward. Your nipples may even be misshapen after pumping—not a good sign! 

If your flange is too large, too much of the areola gets pulled into the flange tunnel when you’re pumping, which can be painful. Likewise, you may feel like your breast pump just isn’t getting the job done.

Not sure what size you need? Call on a certified lactation consultant for advice.

There’s no “forever” fit

Like your breasts, your nipples may change throughout your breastfeeding journey. A flange that fits when baby is one week old may not work as well when she’s three months old. Check the flange fit from time to time, especially if you start to notice discomfort during pumping.

What’s more, some women need to switch to a larger flange size mid-pump because their nipples naturally expand from the suction. (Totally normal, by the way.)

Lansinoh has a range of five flange sizes to choose from. Breast flanges are usually measured in millimeters, referring to the diameter of the tunnel. Lansinoh’s standard size is 25mm, and additional sizes offered are 21mm, 28mm, 30.5mm, and 36mm.)

Fit for a queen

Pumping is hard work, and you want to get the most out of every pumping sesh. Lean on tips and tools that make pumping easy, efficient, and comfortable.

Here’s to finding your “Goldilocks” flanges—not too big, not too small.


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