The Impact of Pump Flange Size on Milk Output and Comfort: A Look at Recent Findings

The most effective milk removal happens when the nipple is comfortably stimulated and comfortable vacuum pressure is applied to the face (tip) of the nipple. Traditional sizing of flanges often discourage the nipple from gliding along the tunnel of the flange and allows the vacuum to extend to the whole nipple as well as some of the areola.

Prolactin is the hormone that stimulates breast/chest tissue development and is responsible for milk production. One of the most potent stimuli for prolactin synthesis is nipple stimulation. Using the right size flanges that allow each nipple to touch the flange tunnel and glide back and forth during pumping ensures adequate and comfortable nipple stimulation.

Oxytocin, the hormone responsible for (among other things) milk ejection reflexes (also known as let-downs), is activated by sensory nerves. These are the nerves that (among other things) are activated by pleasant and comfortable touch. In the case of breast/chest feeding, this happens when there is comfortable rubbing/gliding along the sides of the nipple and there is comfortable, pleasant vacuum pressure applied to the nipple tip.

When comfortable vacuum pressure is applied just to the nipple tip, less vacuum pressure is usually needed for effective milk flow, thereby resulting in a much more comfortable pumping experience. This is because the outlets from the milk ducts are usually at the tip of the nipple, and concentrating the vacuum to just that area decreases the swelling to other parts of the nipple that may ca use less milk flow and nipple pain. Occasionally, a lactating parent may have a milk duct ending on the side of their nipple, but this is not very common. In this case, using a slightly larger flange on that breast/chest will allow milk to flow easily.

Lisa A Anders et al published a comparative pilot study of traditional versus a new way to size pump flanges in the Feb 2025 issue of the Journal of Human Lactation. Check it out here: https://pubmed.ncbi.nlm.nih.gov/39614713