As a general rule, mummy's nipples may become more erect/swollen after pumping, hence we would highly recommend mummies to provide an allowance of at least 3-4mm in the selection of flanges. This is to prevent the nipple from rubbing against the nipple tunnel post-pump, etc.
If you have a nipple measurement of 18mm, the 22mm flange would be suitable. (18mm + 4mm = 22mm)
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