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Size DOES Matter

Choosing the breast shield size that’s right for you.

Any breastfeeding mom will tell you that pumping is hard work. There's a saying ... "Work smarter, not harder".  Using every brain cell you have won't make pumping the easiest thing you've done, but making sure that your equipment is right for you is a HUGE start.

When a baby is breastfeeding, the gums are positioned beyond the base of the nipple where they use compression.  This, along with suction, negative pressure, the movement of the tongue and many muscles, aids in the efficient removal of milk.  A pump, on the other hand, simply creates a vacuum that forms a pressure gradient.  With pumping, milk is actually pushed out of the breasts and, unless you are a science or physics nerd, that process is too complicated to explain right here, so I won’t.  NOTE: This is why you can’t determine how much milk your baby is getting by pumping. It’s not the same, don’t do it. It will just make you worry. The bottom line is that, contrary to what seems to be happening, a pump doesn’t suck or pull milk out of the breast.

Because of the above facts, it is so very important to have the right size breast shield.  Not only will the wrong size cause discomfort, or downright pain, it can decrease the amount of milk you will pump … which will lead to a decrease in milk supply over time.  Just like breastfeeding, pumping shouldn’t hurt. Moms who have pain while pumping are either 1) pumping at a setting that is too high or 2) using an ill-fitting breast shield, or 3) both.

Determining the right size for you is actually easy, once you know what you are doing.  Breast shields come in various sizes based on millimeters.  The smallest available is 10mm and the largest is 40mm. Measuring the diameter of the base of your nipples (see the infographic below) can help you determine which shield size will probably fit. Then, you need to pump and see what your nipple is doing.  While pumping at a comfortable vacuum-setting, you need to watch your nipple and areola moving in and out of the “tunnel”.  With the right size, you will:

  1. see your nipple moving freely, without the sides touching or rubbing inside the tunnel. If it is rubbing, you need a bigger size.

  2. see only about one-eighth (2mm) to one-fourth (5mm) of an inch of your areola going into the tunnel with your nipple. This is measured from the base of the nipple, back. If more than one-half of an inch of the areola is going into the tunnel (you will probably see a good bit rubbing on the sides), then this shield is too big and you need to go smaller.

  3. notice that the “bend” from tunnel to funnel will be positioned behind the nipple (like baby’s gums)

  4. not experience any pain or discomfort.  The wrong size shield can actually damage the base of the nipple or the skin.

Breast Shield Size

Infographic courtesy of Medela

You should be aware that during your breastfeeding/pumping journey your breasts and nipples may change.  Hence, the size shield that you need may also change.

Having the correct breast shield size is just one of several things that can make or break a successful experience. If you are unsure which shield size you need, or if you are having other pumping issues, contact an IBCLC.  I frequently do pumping consults with moms to determine correct flange size, educate about the operation of their particular pumps and come up with a pumping plan to fit their needs.

Keep Calm and Pump on!


The Breastfeeding Guru

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