How to Know What Size Flange to use With Your Breast Pump

By Marina Macleod

January 6, 2020

Marina is a Registered Nurse with over 14 yrs of experience, a Mama Coach in Calgary, AB and area and a Mama to 2! She offers prenatal education, newborn and post-partum support, lactation counseling, infant & child CPR/Choking workshops, as well as sleep education programs based on science, empathy & support.

PUMPING. If you are pregnant or have a newborn then pumping is something you have likely considered or started! It is probably a new technique for you and it is completely normal to feel unsure. There are so many products available on the market for pumping breast milk it can certainly be overwhelming. This article will take you through the process of how to know what size flange to use with your breast pump to properly fit your breast to express milk appropriately without damaging your breast tissue or nipple area.

What is a Flange?

The flange (or breast shield) is the plastic funnel-like part of your pump that is placed on your breast. This will create a seal and allow suction for milk to be efficiently expressed and collected. They are usually available in 21mm, 24mm, 27mm, 30mm and 36mm sizes. The sizes could also be categorized into small, medium, large or extra large depending on the make and model of your pump. NOTE: The size in millimeters describes the diameter of the tunnel and not the larger funnel-like portion of the shield.

How do you measure your nipple to determine the correct size flange?

Most importantly, the correct fit is determined by the size of your nipple NOT the size of your breast. Take a tape measure or ruler and measure the diameter at the base of your nipple (where your nipple tissue meets your areola) in millimeters, but do not include the areola. Make note of the number you measure. This measurement will be used to determine what size flange is the best fit for your breast based on the manufacturer’s recommendations. Each brand of pump should have directions on what size flange corresponds to the diameter of your nipple. For example, if you have a Medela pump and you measured 22mm at your nipple base then the 24mm flange would be the appropriate size for you!

Source: Medela 2020

What should a correct fit look like?

  • Your nipple should be centered in the middle of the tunnel
  • Your nipple should move FREELY when the pump is on and not rub on the sides of the tunnel
  • Only your nipple should be inside the tunnel or very minimal areolar tissue, no extra areolar or breast tissue should be present in the tunnel
  • You should see and feel a gentle rhythmic motion on the breast tissue while the pump is working
  • Your breast should feel softer with adequate emptying of the breast achieved
  • There should be no nipple breakdown or trauma present

A good acronym to remember when choosing a proper fitting flange is COMFY.

C- Centered nipple
O- Only minimal areolar tissue in the tunnel
M- Motion of breast is gentle and rhythmic
F- Feels comfortable
Y- Yields an empty breast

What does an incorrect fit look like?

  • You experience any discomfort or pain while pumping
  • You notice blanching (or whitening) of your nipples
  • You notice a white or red ring around the base of your nipple where the tunnel meets the flange
  • You are not getting adequate milk expression
  • You do not see or feel a rhythmic motion when the pump is working
  • If you place the flange on your breast and your nipple is snuggly touching the sides of the tunnel before even turning the pump on, you will need to size up
  • If when you are pumping you notice your nipple and areola (more than just the minimal tissue around your nipple base) are being sucked into the tunnel and your nipple is even touching the end of the tunnel, you should size down.

Keep in mind that your breast shape and nipple size may change throughout your breastfeeding journey. So be sure to reassess and look for changes regularly.

If you have questions or would like support in determining how to know what size flange to use with your breast pump contact a Mama Coach in your area. Breastfeeding journeys look different for everyone, just know YOU are doing amazing Mama!

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