Breast Shield Sizing: How to Get the Best Fit

When pumping, choosing the right breast shield size is extremely important. That is why we’ve assembled our breast shield sizing guide to take you through all the flange sizing basics, including how to measure yourself to ensure correct sizing, a breast shield size chart, warning signs of an incorrect fit, and more.

Why Correct Breast Shield Sizing Matters

It’s not just a matter of comfort – using the correct size of breast shield while pumping is vital for efficiency, too. Your goal is to get the most out of your sessions as possible, and a breast shield that’s too large or too small can negatively impact the amount of milk you’re able to pump. Even if you’re a pro and have been pumping for a while, keep in mind that your breast shield sizing can change throughout your breastfeeding journey – and your pumping routine might benefit from a reevaluation and resizing. You might even find that each breast needs a different shield size. Remember, pumping shouldn’t hurt! The following information will help you choose the right breast pump flange size for your needs.

Understanding Medela Breast Shield Sizes

How to Measure Your Nipple for Your Flange Size

The starting point for choosing the correct breast shield is determining your optimal size based on your nipple diameter.

  • Using a ruler or measuring tape, measure the diameter (or distance straight across the middle) of your nipple at the base in millimeters. Do not include your areola. (Tip: Not in a “math” mood? 1 cm = 10 mm.)

  • Based on your measurement, use the guide below to view Medela PersonalFit™ and PersonalFit PLUS breast shield sizes to determine which one is the right fit for you:

  • If your nipple measures 16 mm in diameter, your recommended breast shield size is 21 mm. This is because the 21 mm shield fits nipples up to 17 mm in diameter. If your nipple diameter measures 24 mm, your recommended size would be 30 mm.

Note that our PersonalFit Flex™ breast shields are available in four sizes – 21mm, 24mm, 27mm, and 30mm. We offer a 36mm size in PersonalFit and PersonalFit PLUS only, but not in PersonalFit Flex.

Test Your Breast Shield Sizing

Since your breast shield flange size is also dependent on breast tissue and skin elasticity, it’s important to confirm you’ve chosen the correct size for your Medela nipple shield. Here’s how to check:

  • Using the 24 mm breast shields included with your pump (or the size chosen after measuring your nipples), center your nipple and gently hold the breast shield against your breast. (Note: pressing breast shields too hard against your breasts when pumping can block your milk ducts.)
  •  Adjust your breast pump’s vacuum for Maximum Comfort Vacuum™ to achieve optimum suction level, turning the vacuum up until slightly uncomfortable and then down one notch.

When your breast shield fits correctly, your nipple will be centered in the breast shield tunnel and will move freely during pumping. Refer to the images below while pumping:

Determining if You Need a New Breast Shield Size

You will need to re-evaluate your breast pump flange size if you find that one or more of the following are happening while you’re pumping:

  • Your nipple is rubbing the sides of the breast shield tunnel to the point of causing discomfort.
  • You see excessive areola being pulled into the breast shield tunnel.
  • You have redness on or at the base of the nipple during and/or after pumping.
  • Your nipples or areola are turning white during and/or after pumping.
  • Your breasts still feel full after pumping.

If you have more questions or need further help with breast shield sizing, reach out to a Certified Lactation Consultant. In the long run, it’s worth taking the time to determine the breast shield size that’s right for you. You’ll benefit by maximizing your pumping sessions so you can provide for the one who matters most – your baby!

Watch the full video below for even more helpful information and sizing tips:

Choosing Your Breast Shield Size

Fast relief for sore nipples and dry skin.
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