A breast pump flange, sometimes called a breast shield, is the funnel-shaped piece of plastic or silicone placed directly over the nipple and breast when pumping. Its primary function is to create an airtight seal around the areola, allowing the pump’s vacuum to gently draw the nipple into the tunnel for milk extraction. The correct fit is important because it directly impacts both comfort and the efficiency of milk removal. An improperly sized flange can lead to tissue damage, pain, and significantly decrease the volume of milk expressed.
Visual and Physical Indicators of a Flange That is Too Small
A flange that is too small creates immediate signs of restriction and friction on the nipple tissue. The most obvious indicator while pumping is the nipple rubbing painfully against the sides of the tunnel as the vacuum pulls it in and out. This abrasive contact can lead to chafing, cracking, and abrasions on the nipple skin. The areola, the darker skin surrounding the nipple, may also appear swollen or pushed tightly against the opening of the flange.
When a flange is too restrictive, the nipple cannot move or expand properly, impeding the flow of milk from the ducts. Post-pumping, the nipple may appear visibly red, swollen, or bruised at the base due to compression. A more concerning sign is nipple blanching, where the tip turns white due to restricted blood flow, a condition known as vasospasm.
The pain experienced is typically sharp, pinching, or squeezing, occurring with every cycle of suction. This discomfort causes the body to release stress hormones, which actively interfere with the oxytocin reflex needed for milk let-down. This hormonal interference, coupled with physical restriction, often results in noticeably low milk output and incomplete breast drainage. Consistently using a flange that is too small can contribute to complications like clogged milk ducts or mastitis.
Identifying When a Flange is Too Large
Symptoms of an oversized flange can sometimes be mistaken for the opposite problem. When a flange is too large, it allows too much of the areola to be pulled deep into the tunnel along with the nipple. Ideally, only the nipple and a minimal amount of areola should be drawn in; excessive pull-in indicates an improper fit.
This excessive tissue pull-in leads to a less efficient vacuum seal. This may feel like a slow, uncomfortable “chugging” sensation rather than the smooth, rhythmic flow of effective expression. The pain is often described as a dull discomfort or chafing at the base of the nipple and areola, contrasting with the sharp pain of a small flange. Drawing too much areola into the tunnel can compress milk ducts, leading to reduced milk yield and incomplete breast drainage.
Steps for Determining Your Correct Flange Size
The foundation of finding the correct flange size is accurately measuring the nipple diameter before pumping begins. Measure when the nipple is relaxed, not after a pumping session, as tissue is often temporarily swollen or elongated afterward. Use a ruler or specialized tool to find the diameter across the base of the nipple, excluding the areola. This measurement should be taken in millimeters (mm) and is the most reliable indicator for sizing.
You should measure both nipples, as they are commonly different sizes, which may necessitate using two different flange sizes. Once the diameter is obtained, the general guideline is to select a flange size that is 2 to 4 millimeters larger than the measured diameter. For example, an 18 mm nipple would typically require a 21 mm or 22 mm flange.
This small margin allows the nipple to move freely within the tunnel without rubbing against the sides, promoting maximum milk removal. If discomfort or poor output persists after self-measurement, seeking assistance from an International Board Certified Lactation Consultant (IBCLC) is recommended. An IBCLC can perform a visual assessment while you pump, which is often the most accurate method for confirming the appropriate size.