How to Tell if Your Breast Pump Flanges Fit

Woman using a breast pump

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When you're breastfeeding, a breast pump can be very useful. It allows you to express breast milk and store it so your baby can feed when you're apart. When choosing a pump, it's important that the flange (also called a breast shield) fits you properly. One that doesn't can cause soreness and injury and reduce the amount of milk you produce.

The Standard Breast Pump Flange

The breast pump flange is the part that connects your breast to the pump. Milk will travel down the tube to the bottle or another collection device.

After you give birth and while you're pumping, it's normal for your breast to change size, so you may need multiple flanges for your pump. It's also a good idea to check the fit from time to time.

All breast pumps come with at least one average-sized breast pump flange. The average flange is between 24 and 27 millimeters (mm), which corresponds to the size of your nipple. But not all women fit into these sizes and you can get smaller or larger flanges. The sizes range from 21 mm to 36 mm in the plastic flanges and there is a 40 mm glass flange available.

Why Size Matters

Not having the right size breast pump flange can result in problems. For instance, you may not be getting the most amount of breast milk possible and this may lead to blocked milk ducts. A poor fit may also cause nipple damage, including rub marks and cuts on the nipple.

Many women notice a difference almost immediately after finding the right sized flange. The first thing that they notice is that using the breast pump is more comfortable. After that, the amount of breast milk that they are able to pump begins to increase.

How to Tell If Yours Is a Good Fit

Nearly every breast pump manufacturer will offer a size guide for breast shields and these are good to review before buying a breast pump. The Food and Drug Administration (FDA) recommends researching the manufacturer's flange size options as well . This will give you a good idea if you can order a different size if you find that you need one.

The size of the flange you need is the size of your nipple. You can measure yours using a ruler or measuring tape. Be sure to measure the diameter of the nipple alone and do not include the areola. The Medela website has a good diagram with instructions on how this is done.

When you get your pump, you can tell that the flange is a proper fit if:

  • You are not experiencing pain in your nipple.
  • You do not see a white circle at the base of the nipple, nor should your nipple blanch.
  • You don't feel areas of the breast that still have milk inside. This indicates an uneven removal of milk.
  • Your areola should have little or no tissue inside the tunnel of the breast pump.
  • Your nipple is centered in the flange and moves freely in the tunnel of the breast pump.

When You Need a Different Size

If you don't have the right size, you will want to see if your breast pump came with other flanges or if you will need to order flanges.

If you go up in size, you may be restricted from using some of the softer plastic flanges, like those found on the Avent Breast Pumps and others. With some manufacturers, the smaller flanges actually fit inside the average-sized flange.

Most breast pumps will only come with a 24 mm size flange. The other sizes may be available and are sometimes sold as a set of various sizes. Some manufacturers may only offer the more common sizes (24 mm to 29 mm).

Women with other size needs may have to purchase from other sources that do not make their pump. This can lead to concerns about whether or not the new flanges will work adequately with the pump. The good news is that most will work without a problem.

Finding Help

If you are having trouble trying to figure out what size you need, even with the guidelines, it is perfectly fine to ask for help. A lactation consultant can be of great help.

If you do not already have a relationship established with a lactation consultant, call the hospital where you gave birth. It's typical that they will have someone who is registered with the International Board of Lactation Consultant Examiners (IBCLC) that can help you determine the issue with sizing. You can also try a local store that specializes in breastfeeding products.

A Word From Verywell

Finding the right flange for your breast pump can make your experience less painful and more productive. Though it may be frustrating at first to find the right size, the right one for you is available, and ensuring a proper fit will be worth it.

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Article Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Becker GE, Smith HA, Cooney F. Methods of milk expression for lactating women. Cochrane Database Syst Rev. 2016;9:CD006170. doi:10.1002/14651858.CD006170.pub5

  2. U.S. Food and Drug Administration. Choosing a Breast Pump.

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