A breast pump flange, also known as a breast shield, is the funnel-shaped part of a pump that creates a vacuum seal around the nipple and areola to draw the nipple into the tunnel for milk extraction. Most pumps include a standard 24-millimeter (mm) flange, but nipples come in a wide range of sizes, meaning a correct fit is often a personalized process. Finding the right size is necessary for both comfort and efficiency during pumping sessions. This guide provides practical steps for measuring your nipple and identifying the correct flange size.
Why Accurate Sizing is Critical
The diameter of the flange tunnel directly impacts how much milk you can express and how your breast tissue is treated. An improperly sized flange can significantly reduce milk output because it fails to adequately stimulate the breast for milk removal. If the flange is too small, it can constrict milk ducts, leading to inefficient emptying, reduced supply, and potentially clogged milk ducts.
A flange that is too small causes the nipple to rub painfully against the sides of the tunnel, resulting in friction, blistering, bruising, or cracking of the delicate tissue. Conversely, a flange that is too large can pull in too much of the areola, causing swelling and discomfort, or fail to create the necessary vacuum seal for effective suction. A correct fit helps ensure a more comfortable and sustainable pumping experience.
Measuring Your Nipple Diameter
To accurately determine your flange size, you must first measure the diameter of your nipple in millimeters (mm). The most precise measurement is typically taken after a pumping session, as the nipple expands slightly once stimulated. You will need a ruler or measuring tape with millimeter markings, and it can be helpful to use a mirror or a printable sizing guide.
Measure the nipple across its base, which is the widest part where it meets the areola. The measurement must only include the nipple itself and exclude any part of the areola. It is important to measure both nipples separately, as they are often different sizes, meaning you may need two different flange sizes.
Once you have the diameter of the nipple in millimeters, you can calculate the suggested flange size by adding a small amount of extra space. The general recommendation is to add 2 to 4 mm to your measured nipple diameter. For example, if your nipple measures 16 mm in diameter, the ideal flange size would be 18 mm to 20 mm. This added space allows the nipple to be gently drawn into the tunnel and move freely without rubbing against the sides.
Signs of an Incorrect Flange Fit
Even with careful measurement, the fit must be confirmed by observing your body during an actual pumping session. A correctly sized flange shows specific visual cues while the pump is running. The nipple should be centered in the flange tunnel and move back and forth gently with the pump’s suction without rubbing the sides. Only a minimal amount of areola should be pulled into the tunnel, and the breast tissue should move rhythmically.
If the flange is too small, the nipple will rub painfully against the tunnel walls, or it may appear constricted and turn white or red after pumping. If the flange is too large, a significant portion of the areola will be pulled into the tunnel, or the nipple may be pulled all the way to the end of the tunnel. A white ring around the base of the nipple, known as blanching, indicates that the flange is too small and restricting blood flow.
Sensory cues are equally important for troubleshooting a poor fit and should be the primary indicator of comfort. You should not experience any pain, pinching, or bruising while pumping. If you feel a sharp, shooting pain or notice a squeezing sensation, the flange is likely the wrong size. If your breasts still feel full or heavy after a standard pumping session, the inefficient milk removal indicates that the flange is not allowing for complete drainage.
Specialized Flanges and Professional Help
Standard hard plastic flanges may not provide an ideal fit for every individual, especially for those with anatomical variations or elastic nipple tissue. Specialty options, such as soft silicone inserts, can be placed inside a larger hard plastic flange to reduce the tunnel size in smaller increments. These inserts are available in a wide range of sizes, often as small as 11 mm, and can help achieve a more precise and comfortable fit.
Other alternatives include flexible flanges made entirely of silicone or those with an oval shape, which can conform better to breasts that do not fit well into a standard round tunnel. Sizing is not always a one-time event, as nipple size can change over the course of the pumping journey. Re-evaluate the fit periodically, especially if you notice a change in comfort or milk output.
If you experience persistent pain, have a consistently low milk supply despite correct technique, or struggle to find a comfortable fit, seek professional assistance. International Board Certified Lactation Consultants (IBCLCs) specialize in flange fitting and can perform a clinical assessment, including observing you pump, to help determine the optimal size and type of flange. Consulting with an IBCLC ensures that complex sizing issues or underlying factors are properly addressed.