How to Master Breast Pump Flange Fit

Proper fit is always important, and that’s especially true when it comes to breast pump flanges aka breast shields. Lactating parents who have breast pump flanges that are too small or too large can experience soreness, irritation, and even clogged milk ducts. Meanwhile, flanges that are the proper size mimic a baby’s latch, and lead to maximum comfort and milk output.

First Things First, What is a Flange?

Flanges or breast shields are the cone-shaped plastic pieces of a breast pump, worn over your nipples to create a gentle vacuum for milk extraction. 

How Can You Tell if Your Flange is Too Small?

Flanges that are too small may cause excess friction, pinching, or squeezing as the nipple is pulled against it. As a result, your nipple or areola could become white or discolored, and you could experience low milk supply or painful milk extraction.

… And How Can You Tell if Your Flange is Too Big?

If your flanges are too large, your areola will be pulled into your pump’s breast flange tunnel, which can cause discomfort, as well. It’s also possible that your areola won’t receive enough stimulation, which could cause delayed onset low milk supply.

So How Should a Breast Pump Flange Fit?

To find the correct size, you’ll need to measure both nipples (oftentimes, they’re not symmetrical!). Using a ruler or measuring tape, measure the diameter of your nipple, excluding your areola. Flange measurement systems are typically in millimeters, so know that 1cm = 10mm.

Then select your flange size based on your nipple measurement. According to Motif Medical:

• If you measured up to 17mm you’ll fit in a 21mm flange.
• If you measure up to 22mm use size 24mm.
• If you measured up to 23mm select size 27mm.
• If you measured up to 26mm use 30mm.
• If you measured up to 32 mm use size 36 mm.

A flange that’s the correct size will allow your nipple to fit centered in the flange’s narrow tunnel, without any rubbing on its walls. Other signs that you have the right-size flange include: your areola does not get sucked up into the tunnel of the breast pump; after pumping, there is no remaining milk in parts of your breast (which could indicate uneven extraction); and you don’t experience nipple pain or discoloration.

Also be aware that it’s common for your nipple size to change throughout your breastfeeding journey, so it’s a good idea to have a small range of flange sizes on hand!

Talk to Your International Board Certified Lactation Consultant

Your IBCLC is the expert when it comes to comfortable, effective flanges. Ask them to assist you with determining your perfect breast pump fit, according to your unique nipple shapes and the density of your areolas. Whether you’re a new parent or a pro, flange fit can be tricky—but it’s one of the most essential components to pumping successfully and sustainably. Remember, you deserve to be comfortable, and the more relaxed you feel while pumping, the better for everyone!