Wearable breast pumps have become a popular choice for parents who want convenience and freedom while pumping. These hands-free devices allow you to pump discreetly while moving around, working, or caring for your baby.
While convenience is a major benefit, many parents overlook one of the most important factors for success: sizing. The right size ensures comfort, proper suction, and efficient milk expression. The Ameda GLO comes with 24mm flanges and includes 17mm, 19mm, and 21mm soft inserts. Additional Ameda Universal Soft Flange Inserts are available in sizes 11mm–21mm to help you find your best fit.
This guide will walk you through why sizing matters, how to measure correctly, and what to watch for when using a wearable breast pump.
Why Sizing Matters for Wearable Breast Pumps
Choosing the correct flange or flange insert size (the part that sits on your nipple) is what drives comfort, suction seal, and milk output—not the overall size of the wearable pump itself. A good fit helps you pump comfortably and efficiently; a poor fit can cause rubbing, pinching, or reduced milk flow. For GLO, sizing is achieved with flange inserts that sit inside the standard 24 mm flange (17 mm, 19 mm, and 21 mm included; additional inserts available 11–21 mm).
Comfort and Fit
When your flange or flange insert fits correctly on your nipple, pumping should feel natural and comfortable. If the flange/insert is too large, excess areola or breast tissue can be pulled into the tunnel and rub; if it’s too small, the nipple can pinch or scrape the sides, causing irritation or damage. Fit is determined by nipple diameter, not overall breast size.
Milk Expression Efficiency
A correct fit ensures that the pump creates the right amount of suction without discomfort. This is crucial for achieving milk flow and efficiency. If your breast pump flange or flange insert isn’t the correct size, it can lead to lower milk output, which can be frustrating and discouraging. If the flange/flange insert is too large, breast tissue can be pulled into the tunnel, reducing efficiency. If too small, the nipple may rub against the sides, causing friction and lowering output.
Long-Term Health
Repeated use of a pump flange that isn’t the right size can result in long-term issues such as clogged ducts or nipple trauma. Proper sizing ensures that breast pumps work effectively without causing pain or complications over time. Ameda recommends replacing flange inserts every 3 months, or sooner if damaged, to maintain comfort and performance
Key Components of Pump Sizing
The primary factor that determines fit is the flange or flange insert size that sits on your nipple—not the overall pump or cup size. Choose size by nipple diameter, then match to the nearest insert so the nipple moves freely without rubbing.
Flange Size
Flange size is determined by nipple diameter, not breast size. Use a flange measuring guide or ruler to measure the diameter of your nipple (not the areola) after pumping or nursing, then select the closest available flange or flange insert size.
Pump Design
The Ameda GLO design allows use of multiple flange inserts (11–21mm) inside the standard 25mm flange to create a customized fit.
How to Find the Right Flange Size
Correctly measuring your nipple diameter is key to finding the right flange size for your wearable breast pump.
Measuring Nipple Diameter
To measure your nipple for flange sizing, measure your nipple diameter at the base, after a pumping or nursing session. Select the insert size that is slightly larger than your nipple diameter to allow free movement without rubbing.
Common Size Ranges
Keep in mind that sizing is not universal, so it’s important to try different sizes to find the best one for you. Ameda Universal Soft Flange Inserts are available in sizes 11mm, 13mm, 15mm, 17mm, 19mm, and 21mm. The Ameda GLO comes standard with 24mm flanges plus 17, 19, and 21mm inserts (27mm flanges are available for purchase separately).
Signs of an Incorrect Fit
If your flange size is wrong, you may experience discomfort, pinching, or a decrease in milk flow. Other signs include whitening of the nipple tip, excessive areola being drawn into the tunnel, or pain during pumping.
Differences Between Traditional and Wearable Pump Sizing
Many women transitioning from traditional breast pumps to wearable breast pumps notice that sizing can feel different. Ameda GLO is a wearable pump with an integrated cup with built-in flange. Having integrated cups is common in wearable breast pumps and this differs from traditional pumps, where flanges of multiple sizes are attached externally (not built directly into the pump).
Common Mistakes to Avoid
Sizing mistakes can result in discomfort and inefficiency when pumping. Here are some common errors to avoid.
Relying on Default Flange Sizes
Many wearable pumps include a standard 24 mm flange, but that size doesn’t fit everyone. Ameda GLO includes 24 mm flanges plus 17 mm, 19 mm, and 21 mm inserts in the box, and additional flanges (27 mm). The Ameda Universal Soft Flange Inserts are available in 11–21 mm to help you find your best fit.
Ignoring Discomfort
Pumping should not hurt. If you feel rubbing, pinching, or pain, stop and reassess your flange insert size. If irritation or discomfort occurs, discontinue use and consult your healthcare provider.
Skipping Sizing Adjustments
As your body changes, especially postpartum, it’s important to reassess your flange size. Many women find that their breast size and nipple shape change over time, requiring new sizing.
How to Get the Most from Your Ameda GLO Wearable Breast Pump
Below are a few tips to ensure your wearable breast pump provides maximum comfort and efficiency.
Reassess Regularly
Your fit can change over time, especially postpartum. Reassess your flange/flange insert size periodically and whenever you notice discomfort or a decline in milk output
Try Different Flanges
If the current setup doesn’t feel right, try a different insert size. GLO ships with 17 mm, 19 mm, and 21 mm inserts. Ameda Universal Soft Flange Inserts are available in 11–21 mm
Use a Lactation Consultant
If you’re struggling to find the right size, a lactation consultant can provide guidance and ensure you’re using the correct flange size and pump settings for your body. The NEST and The Lactation Network are two of Ameda’s trusted partners.
Ameda’s Approach to Flange Sizing and Support
At Ameda, we understand every parent’s body is unique. The Ameda GLO Wearable Breast Pump includes 24 mm flanges plus 17 mm, 19 mm, and 21 mm inserts. For an even more precise fit, Ameda Universal Soft Flange Inserts are available in 11 mm, 13 mm, 15 mm, 17 mm, 19 mm, and 21 mm to help you find your best size.
Ready to find your best fit? Explore Ameda’s Universal Soft Flange Inserts (11–21 mm) and the GLO Wearable Breast Pump. Always follow the Ameda GLO Instructions for Use for detailed sizing, cleaning, and usage guidance.
Contact us today for more information.