When it comes to pumping, one of the most important decisions you’ll make is selecting the right flange. It might sound simple, but choosing the correct size can have a huge impact on your comfort, milk output, and overall experience. But don’t worry—finding the right fit is easier than you think, and we’re here to help you every step of the way!

What is a Breast Pump Flange?

A breast pump flange (also known as a breast shield) is the plastic or silicone piece that fits over your nipple and areola during pumping. It forms a seal that helps the pump effectively draw out milk. While most pumps come with a standard 24mm flange, you may find that a different size works better for your body, depending on your unique anatomy and your pumping experience.

Why is the Right Flange Size Important?

Having the correct flange size is crucial for ensuring proper pump function and effective milk removal. If your flange is too small or too large, you may face issues like:

• Nipple pain or damage
• Lower milk supply
• Engorgement, plugged ducts, or mastitis
• Less effective pumping

Choosing the right flange size not only helps you avoid these problems but also ensures that pumping is more comfortable and efficient. When your flange fits properly, it creates a strong, consistent suction without causing discomfort or irritation. This means you can express milk more effectively and avoid damage that can occur with the wrong fit. 

Available Flange Sizes

Flanges come in a range of sizes, typically from 10mm to 40mm. Here’s a quick breakdown of what’s available:

• Standard Flanges: 24mm is the most common size included with many pumps, but most pump manufacturers offer a range of sizes, including both smaller and larger options, to better suit your individual needs.
• Inserts: Some pumps come with silicone or plastic inserts to reduce the size of a 24mm flange, making it more customizable.
• After Market Parts: If you find that the flanges or inserts provided with your pump aren’t quite the right fit, there are plenty of aftermarket parts that can help. Many brands offer flanges and inserts in various sizes and materials, giving you the flexibility to customize your pumping experience for maximum comfort and efficiency.

When to Measure

Your breast size and shape can change during pregnancy, postpartum, and as you continue your breastfeeding journey. Because of this, your flange size might change too.

• Measuring your nipple a week or two before delivery will give you a good starting point in case your baby is unable to breastfeed for any reason, such as a NICU admission. 
• Your most accurate measurement will be around 2 weeks after your baby is born, but keep in mind that this can change at any time.  
• If you notice that pumping becomes uncomfortable or your sessions feel less effective, it might be time to recheck your flange size. This will help ensure your pumping experience stays comfortable and productive.

How to Measure

• Don’t Pump or Breastfeed Right Before Measuring: It’s best to measure your nipple size when you’re not feeding or pumping. Gently roll your nipple to stimulate, but avoid pumping beforehand.
• Use a Measuring Tool: You can use a measuring tape, a silicone nipple measuring tool, or even a printable measuring ruler to get the most accurate measurement.
• Measure Your Nipple Diameter: Measure your nipple at its widest point, typically at the base. Record the measurement in millimeters.
• Measure Both Nipples: It’s common for moms to need different flange sizes for each breast, so make sure to measure both sides.

The COMFY Test

Finding your nipple size is a good place to start, but a pumping trial is just as important to determine function along with fit. Use the acronym “COMFY” to help determine your flange size. This term was specifically designed to help moms remember the 5 major guidelines for breast shield sizing:

• C – Center Nipples Behind the Flange Opening
  • Your nipple should move in the tunnel without swelling, color change or pain.
• O – Only the Nipple Should Enter the Flange Tunnel
  • Many moms find the most comfortable and effective flange is closely fitted to the nipple diameter.
• M – Motion of Your Breast is Gentle and Rhythmic
  • There should be no loss of suction resulting in a sudden release of the breast tissue at the end of each cycle.
• F – Feels Comfortable 
  • Your breast pump shouldn’t cause any pain, discomfort, or tenderness.
• Y – Yields Well-Drained Breasts
  • Your breasts should feel softer and lighter after each pumping session.

The Bottom Line: Choose the Best Fit for You

What If I Have Questions?

If you are interested in learning more, these Aeroflow classes expand on some of the topics discussed above:

• Pumping 101
• How to Fit Your Flange

Want More Info?

For a directory of Aeroflow’s other Care Guides offering information on pregnancy, baby care, and more, browse our comprehensive list of titles:

References