I was going back to work and was desperate for a bottle my exclusively breastfed son would not reject.  By "reject" I mean screaming, terrible fits. In the weeks leading up to daycare we had tried every bottle brand out there and finally compromised by using a sippy cup. So, at 9 months old, my no-bottle-yet son started full time daycare. We brought his little sippy cups that he would slowly drink expressed milk from (but still, he was pretty much exclusively breastfed), and hoped for the best. But after 1 week the teachers were frustrated and concerned and suggested we retry the bottle.