Using the correct flange size is incredibly important for your comfort while pumping as well as efficient milk removal.

A Deeper Look:

What are Flanges?

Flanges, or breast shields, are the funnel-shaped pump pieces that fit directly over the nipple and form a seal around the areola (the softer circular bit of skin around your nipple).   This configuration allows for the creation of a vacuum seal that draws the nipple into the tunnel and encourages milk extraction.  If a flange is too big, too much of the tissue surrounding the nipple will be pulled into the tunnel.  If the flange is too small, it may lead to too much friction.  A flange that is too small or too big can lead to swelling, pain, clogged ducts, blistering, and a restricted output of milk.  The right sized flange will likely allow more milk removal and more efficient milk removal.

Flanges are sized in millimeters and range approximately from 13mm to 36mm.  If you are using a correctly fitted flange, your nipple should be able to move freely as it is elongated and pulled down the tunnel, and your areola should rest comfortably at the start of the tunnel portion of the flange, with little of the areola drawn into the tunnel.  Generally, pumps come with one or two standard sizes—often size 24mm and size 27mm—and you will need to purchase any other size needed separately.  Even if you know what size flange you need, know that not all flanges sizes are offered by every pump manufacturer and you may need to get creative with your flange set up. 

Are you pumping with the right flange? Take a look at what is happening while you pump.  If a lot of your areola is pulled into the pump flange tunnel, your flange may be too big.  If the entire nipple rubs against the sides of the pump flange tunnel, your flange may be too small.  However, if you are not feeling any pain and you are able to fully empty your breasts of milk, you do not need to be concerned about your nipple rubbing the length of the flange tunnel. 

(Diagram showing the part of the breast to measure to determine flange size)

To find the right flange size, you should wait to measure your nipples until just before a pump session.  Ideally, you would measure following your biggest break between pump sessions (for most mamas that would be the morning pump).  This is because your nipple may swell while pumping. Use a tape measure to find the diameter of your nipple.  The diameter should be measured from one side of the nipple base to the other side of the nipple base.  Measure both nipples because they may be different sizes!  You can also try the Maymom nipple ruler or buy one from Legendairy Milk.  If you need additional help, look for a local lactation counselor or breastfeeding support group (such as La Leche League).

It is suggested you try a flange size that is 2-4mm bigger than the diameter of your nipple, thus, if your nipple diameter measures approximately:

11mm try using a 15mm flange.
15mm try using a 19mm flange.
17mm try using a 21mm flange.
20mm try using a 24mm flange.
23mm try using a 27mm flange.
26mm try using a 30mm flange.
32mm try using a 36mm flange.

This is just a starting point for identifying your proper size.  You should pump with whatever size feels comfortable to you and provides the most milk flow.  This may mean that you use a different size flange on each breast.  Additionally, you may need to reevaluate your flange size over time—breasts and nipples can change, and what works the first few days postpartum may not work when your supply regulates or 6 months into pumping.  Most importantly, do not pump in a flange size that is causing you pain.  

Lastly, nipples are designed to stretch—after all, that is how milk is removed!  However, sometimes, a nipple may stretch and swell too much and will hit the back of the flange tunnel (near your backflow protector and tubing) while pumping using the proper size flange.  This is what is commonly referred to as elastic nipples.  If you are not experiencing pain or low milk output, keep on keeping on! If you are, and you have already checked your flange size—this is so important because an ill fitting flange can make it seem like you have elastic nipples— try lowering the suction strength, using lubrication, or changing the setup of your flange by using silicone inserts or a softer flange designed for elastic nipples. Click here for more information.

The EP&Me Take:

Using the correct flange size is incredibly important!  One of my most significant initial pumping blunders was that I was using the wrong flange size.  I wrote about my flange-size issues in my Troubleshooting: Pain While Pumping post, so if you’ve already read that post, much of this post will sound familiar!

I was not prepared to pump immediately postpartum (I naively thought I had a few months of maternity leave to learn about pumping!), and I trusted that when the lactation counselor informed me I should use the size 24mm that I was, in fact, a size 24mm.  It never occurred to me that there might be more flange sizes than the two included in the Medela kit provided by the hospital and that perhaps the lactation counselor only picked the size 24mm flanges because the only other size included in the kit was size 27mm.  So the lesson I learned was this: nipples come in MANY sizes; this seems obvious now, but at the time it didn’t occur to my sleep deprived brain.

I pumped using those size 24mm flanges for three and a half months until one day, while perusing a forum for new mothers I learned that pumping should not hurt and that improper flange sizes were a common culprit for pain.  After this revelation, I started to look at the nipple rulers and then into the companies you pay to size your nipple for the proper fitting flange.  Although I felt sure that I was using the wrong size flange, I didn’t feel confident in picking the right size even after using the nipple rulers, so I paid a company to size me (at that time I also planned to transition to the Willow pump and wanted to order the correct pieces, so I was very motivated to get the proper size.  I’ll note here that I was asked to measure before pumping and a few hours after my last pump so that any swelling may have subsided).

After I was sized, it was recommended that I try a size 17mm flange on both sides.  I ordered the flanges and was disappointed to find I was still in pain.  The pain was not any worse than I was used to, so I continued to pump with the new flanges and nearly two weeks later, the pain started to improve.  I realized then, that I had still been in pain because my nipples were damaged and needed to heal.  Looking at my nipples, I realized how swollen they had been.  I even decided to try size 15mm flanges, and as it turns out, the right size for me is 15mm AND 17mm—Yes! Two different sizes!—a far cry from 24mm.  I am a 15mm on my left and a 17mm on my right.  While I think I probably needed a 15mm on both sides once the swelling subsided, for some reason (perhaps only a psychological one) I liked the 17mm on the right side.  I was finally pumping without pain. My favorite brand to purchase flanges from is Maymom.

Even using the right size flange, my nipples still nearly hit the back of the tunnel, so I wondered: Do I have those “elastic nipples” I hear mamas talking about?  Early on in my pumping journey I tried the Pumpin’ Pals flanges to see if they would successfully counteract this issue (Pumpin’ Pals flanges are designed with a more gradual angle from the breast shield funnel into the nipple tunnel and their silicone flanges with Elast+Assist Technology can help improve milk flow for mothers with elastic breast tissue).  Unfortunately, the Pumpin’ Pals flanges did not work for my lifestyle—I could not get them to stay connected to the base connector while I pumped (and admittedly I moved around a good bit), which was a MESS!  Fortunately, because the right size flange had fixed my pain issues, I didn’t need to find an alternative flange to accommodate the elastic nipple issue (elastic nipples are not a problem unless they cause you problems, for more information, click here).  I know many people love Pumpin’ Pals and have great success with their products, so do not let my experience discourage you from trying them!  

A properly fitting flange is more than just the proper diameter, it should also be the most comfortable.  For me, as discussed above, I preferred the one-piece flange over the two-piece flange/base connector set because I could not move around the house as easily with the two-piece set.  I preferred the Medela flanges with their valve and membrane system over Spectra’s duckbill system, so even when I switched from pumping with the Medela Symphony to pumping with the Spectra S1, I bought adaptor pieces to allow me to continue using the Medala flanges. If you are looking for the adaptor, you can find it here. 

When I was pumping using the willow, I had to use inserts because Willow did not make their “flange” (I use quotation marks because it is so different than most flanges) in a small enough size.  Inserts are a great option to try to make flanges you already own fit better.  However, it’s worth noting that if you know you need to use an insert, you will likely want to choose a standard size flange (such as a 24mm or 27mm) so that there is room for the insert.  Maymom makes my favorite inserts!

There are a few other products I did not try but have come across during my initial foray into the EP world:

Beaugen cushions: are a soft funnel-shaped piece that can be inserted into flanges to reduce the friction between your breast and the hard plastic of the flange.  The cushion’s purpose is to make pumping more comfortable, but they can also help a mom who is between flange sizes make a too-large flange fit more comfortably.  You may need a larger size flange if you want to use a Beaugen cushion because the cushions take up approximately 2mm of space in the flange tunnel.

Pumpin’ Pal flanges: Pumpin’ Pal offers a flange with an angled neck that allows you to recline slightly while pumping, which may relieve any strain to your back and neck due to pumping.

LacTeck BabyMotion flanges: these flanges are made of silicone, are soft and non-abrasive, and are designed to mimic a baby’s suckling.  LacTeck BabyMotion flanges are supposed to move better with your breast while you pump, allowing a better seal and making breast massaging easier.

Remember: the most important thing is that you are comfortable and pumping without pain. It is worth the time and effort to figure out your size and the best fitting flange. Good luck mama!

If you are interested in purchasing additional flanges from Maymom, click the links below:
Compatible with Spectra, has a wide bottle neck sizes 19mm and up
Compatible with Spectra, has a wide bottle neck size 17mm
Compatible with Spectra, has a wide bottle neck size 15mm
Compatible with Spectra, has a wide bottle neck size 13mm and 15mm, 2-piece flange
Compatible with many Medela pumps, 1 part of a 2-piece flange 10mm and up (you need to buy the base connector separately)