And (isn't what they say about all of us wearing the wrong bra size?) it appears that many of us are using the wrong size. Research (pdf) suggests that nearly 1/3 of mothers need a larger-than standard flange size. I've heard that Medela will be including two sizes of flanges in their Pump in Styles soon.
How do you know if you're using the right size? Medela suggests mothers use the pump and look for several things:
- Is her nipple moving freely in the tunnel?
- Is minimal or no areolar tissue being pulled into the tunnel of the breastshield?
- Does she see a gentle, rhythmical motion in the breast with each cycle of the pump?
- Does she feel the breast emptying all over?
- Is her nipple pain-free?
I'd note that you can't assess whether the nipple is free in the flange without actually watching as you pump, because the nipple often increases significantly in size when you pump. I have a handy Medela flange fitter (looks like a ruler with cut-out circles), but have found that I misjudge sometimes because the nipple is much smaller when a mom isn't pumping.
Ameda offers a good resource page on this, too, with a couple of pictures to illustrate what it looks like when the flange is too small.