I took a breastfeeding class and the lady teaching the class told us that a lot of live cells cling to the clear plastic Avent bottles therefore your baby doesn't get all the possible nutrients from the breastmilk. Has anyone ever heard of this? I already registered for and received all my Avent bottles. I know I will lose money if I try to return them because I do not have receipts for all of them. Trying to decide what to do about this one.