Accurate breast pump flange sizing is necessary for effective and comfortable milk expression. The flange, or breast shield, is the funnel-shaped part of the pump that creates a seal over the nipple and areola, allowing milk to be drawn out. Using the correct size optimizes milk output, as a poor fit can restrict milk ducts and reduce the volume collected. A flange that is too small causes painful friction, while one that is too large may pull too much of the areola into the tunnel, leading to discomfort and potential tissue damage. A simple nipple measuring tool, often a ruler or sizing card marked in millimeters, helps determine the precise dimensions needed for a proper fit.
Step-by-Step Guide to Measuring Nipple Diameter
Preparation involves ensuring the nipple is in its most relaxed state, typically by waiting at least 30 minutes after a pumping or nursing session. The nipple should be clean and dry, and it is helpful to be in a well-lit area. While some tools feature cut-out circles, a ruler or measuring tape with millimeter markings is the standard instrument for measuring the nipple diameter.
Measure only the width of the nipple across its base, specifically where the nipple tissue meets the areola, and not the areola itself. The measurement must be taken in millimeters, as this is the unit used for flange sizing. Gently compress the base of the nipple to ensure an accurate reading of the widest diameter.
When using a sizing tool, hold it flat against the breast and line up the zero mark with one edge of the nipple. Read the measurement at the opposite edge, which provides the diameter of the tissue entering the pump tunnel. Since nipple sizes can vary, measure each one individually and use the larger measurement to select a starting flange size.
Translating Measurements to Flange Size
The measured nipple diameter is only the starting point for determining the final flange size. To find the appropriate size, a buffer of 2 to 4 millimeters is added to the measured diameter. This added space accounts for the natural expansion of the nipple as it is drawn into the flange tunnel by the pump’s vacuum.
For example, a measured nipple diameter of 17 millimeters suggests a flange size of 19 to 21 millimeters. A 20-millimeter measurement corresponds to a flange size of 22 to 24 millimeters. Note that some manufacturers recommend adding 4 to 6 millimeters, so checking the specific pump brand’s sizing guide is advised.
After selecting a flange based on the calculation, a visual assessment during pumping is required to confirm the fit. The nipple should be centered and move freely in the tunnel without significant friction or rubbing against the sides. Minimal areola tissue should be pulled into the tunnel. If discomfort occurs or milk output is low, the flange size may need minor adjustment even if the initial calculation was followed.
Factors Affecting Nipple Size and Measurement Timing
Nipple size is not static and can fluctuate, meaning the initial measurement is not permanent. The best time to measure is before a pumping or nursing session, or at least 30 minutes after, when the nipple is relaxed. Measuring immediately after pumping or when the breast is engorged can lead to an inaccurate size determination, as the tissue may be temporarily compressed or enlarged.
Hormonal changes throughout the postpartum period are a primary cause of size variation. Nipple size often increases toward the end of pregnancy and peaks immediately postpartum before gradually decreasing as the milk supply regulates. For many, the most significant size changes occur within the first six to twelve weeks after birth.
Pumping frequency and duration can influence tissue elasticity and size over time, especially for those who pump exclusively. Common measurement errors include mistakenly measuring the areola with the nipple or measuring while the nipple is erect due to cold or stimulation. Re-measurement is often necessary if pumping becomes uncomfortable or if milk output declines, as the correct flange size may change throughout the pumping journey.