A flat nipple lies level with the areola or protrudes minimally, even when stimulated, which complicates determining the correct breast pump flange size. The flange, or breast shield, is the funnel-shaped piece that seals around the nipple and areola, drawing the nipple into the tunnel for milk expression. Using the correct flange size is essential for a comfortable and effective pumping experience. An improper fit can lead to pain, nipple damage, and inefficient milk removal, which may ultimately reduce milk supply. Correct sizing ensures the nipple moves freely within the tunnel, allowing for thorough breast drainage.
Understanding Flat Nipple Anatomy and Pumping
Measuring a flat nipple requires assessing its functional, drawn-out state rather than its resting state. The true diameter is not visible at rest, so the measurement must capture the tissue that will be drawn into the pump tunnel. Because flat nipples do not naturally extend outward easily, measuring the flat tissue can lead to choosing a flange that is too small for the fully extended nipple.
If the flange is sized incorrectly, the entire areola may be pulled into the tunnel, especially if the flange is too large for the nipple’s diameter. This excessive draw-in can cause swelling, chaffing, and painful rubbing against the tunnel plastic, resulting in discomfort and hindering the milk ducts. An accurate measurement isolates the nipple tissue, allowing it to rhythmically stretch and compress for optimal milk transfer without causing trauma to the areola. This ensures the pump suction is concentrated on the nipple and milk ducts.
Step-by-Step Measurement Procedure
The measurement process begins by attempting to evert or draw out the nipple tissue to reveal its full diameter through gentle stimulation. You can gently roll the nipple between your thumb and forefinger or apply light pressure to the areola to encourage protrusion. Alternatively, a short trial pumping session of one to two minutes at a low suction setting can draw the nipple tissue out enough to make the base visible for measurement.
Once the nipple is stimulated, use a measuring device calibrated in millimeters (mm), such as a printable sizing ruler or a flexible tape measure, to determine the diameter. The measurement must be taken across the diameter of the nipple base, where the nipple tissue meets the areola. Measure only the nipple tissue, being careful to exclude any part of the surrounding areola.
Note the measurement for each breast separately, as different sizes often require different flange measurements. To determine the initial flange size, add a small allowance to the measured nipple diameter to account for tissue expansion and movement during pumping. Adding 3 to 5 millimeters to the measured diameter is a common recommendation to arrive at the starting flange size. For example, an 18 mm stimulated nipple diameter suggests an initial flange size between 21 mm and 23 mm.
Selecting and Testing the Flange Size
The calculated measurement serves as the starting point for selecting a physical flange, choosing the closest available size to the final calculated number. Because nipple size can change and anatomy is individual, the next step is a test pump to validate the fit. This involves observing the nipple’s behavior visually during an actual pumping session to ensure the size is appropriate.
When the fit is correct, the nipple should be perfectly centered in the tunnel opening before the pump is turned on. Upon suction, it should be drawn smoothly into the flange tunnel, moving back and forth gently and rhythmically without rubbing the sides. A good fit minimizes the amount of areola pulled in, ensuring only the nipple is subjected to the suction and pressure.
Signs of an incorrect fit include the nipple rubbing against the sides (too small) or excessive areola tissue being drawn in (too large). If the flat nipple struggles to maintain its position or does not draw out fully, the flange may be the wrong size or the tissue may be overly elastic. For nipples difficult to center or stabilize, specialized aids such as silicone inserts or cushions can be placed inside the standard plastic flange to reduce the tunnel opening and guide the nipple.