How do I choose the right size?
Well let me start off by saying that if you are using a flange that is too big or too small, it may cause lower milk output. It really is THAT important. The inner diameter of the breastshield or (flange) should be 1-2 mm larger than the diameter of your nipple. AFTER a pumping session or 3-5mm BEFORE a pumping session. You should be able to see free movement of your nipple during pumping and there should be little or no suction of the areola into the tunnel of the breastshield.
EXAMPLE: If your nipple diameter AFTER pumping session is 18 mm, a 19 mm breastshield is best. If your nipple diameter is 18 mm BEFORE a pumping session, you can try a 21 mm breastshield. And don't forget to measure each breast as it is possible to have two different sizes.
How to measure the diameter of your nipple?
Download the nipple caliper file here, print it out, cut through the red line, fold along the green dots then you have made yourself a nipple diameter measuring tool. See below for the finished ruler.
What if I have inverted or flat nipples?
