The breast pump flange (or breast shield) is the funnel-shaped piece that forms a seal around the breast and channels milk into the collection bottle. This component is placed directly over the nipple and areola during a pumping session. Selecting the correct flange size is necessary for both physical comfort and maximizing the efficiency of milk expression. An accurately sized flange ensures the pump mimics the natural mechanics of milk removal, allowing the nipple to move freely without friction.
The Importance of Correct Flange Sizing
Using an improperly sized flange can lead to immediate physical discomfort and long-term issues with lactation health. A flange that is too small can cause the nipple to rub painfully against the sides of the tunnel, resulting in friction, soreness, and potential skin damage like cracking or bruising. Conversely, a flange that is too large may pull excessive areola tissue into the tunnel, causing a painful tugging sensation, swelling, and chafed skin around the nipple base.
Beyond pain, incorrect sizing directly impacts milk removal, which can compromise the milk supply. An ill-fitting flange can prevent the breast from draining fully, which may lead to decreased output, plugged milk ducts, or even mastitis. The proper fit stimulates the breast more effectively, ensuring efficient expression.
How to Accurately Measure Your Nipple Diameter
The first step is to determine the diameter of your nipple in its relaxed state, before any pumping. Pumping or nursing causes the nipple to swell, which would result in an inaccurate, often larger, baseline measurement. You will need a ruler or measuring guide marked in millimeters (mm) and a mirror for an accurate reading.
Measure the diameter of the nipple across its base, where the nipple meets the areola. Measure only the nipple tissue, excluding the areola, as the nipple is the part that must fit comfortably within the flange tunnel. Place the measuring tool gently across the base of the nipple, ensuring it is snug but not compressing the tissue.
Because nipple sizes often differ, measure both breasts independently. Recording the measurements in millimeters for each nipple provides the required information for the next step. Some people find it helpful to gently stimulate the nipple before measuring to help it become erect, providing a clearer measurement of the diameter.
Converting Measurement to Flange Size
Once the baseline nipple diameter is measured, a calculation determines the appropriate flange size. The standard practice is to add 2 millimeters (mm) to 4 mm to the measured diameter. This additional space accounts for the natural swelling of the nipple during pumping and allows it to move freely without rubbing against the sides.
For example, if your measured nipple diameter is 17 mm, the recommended flange size would be between 19 mm and 21 mm. If your measurement falls between standard flange sizes, you should select the closest size that is slightly larger rather than smaller. Always refer to the specific sizing chart provided by the pump manufacturer, as flange sizes can vary slightly between brands.
Recognizing and Addressing Poor Flange Fit
Even with a careful measurement, the final fit must be confirmed visually and by sensation during the actual pumping session. A correctly sized flange allows the nipple to be centered in the tunnel and move back and forth gently without making contact with the walls. You should feel a rhythmic tugging sensation, but never sharp pain or pinching.
A flange that is too small will cause the nipple to rub against the sides of the tunnel, often resulting in a painful pinching or squeezing sensation. You may notice the nipple looks red or bruised at the base after pumping. If the flange is too large, excessive areola will be pulled into the tunnel, which can lead to swelling and discomfort. If issues persist after trying the next size up or down, consulting with an International Board Certified Lactation Consultant (IBCLC) can provide personalized guidance and confirmation of the correct fit.