Its not recommended thanks to nipple confusion.
Its not harmful. Ya it could cause confusion but i didnt use one and my baby still couldnt latch. I used a nipple sheild so thats always an option if your baby doesnt latch right.
I formula feed so I never had an issue with nipple confusion however my daughter never took it lol she spit it out the second we put it in.. kinda happy actually we never had to go through the process of taking it away.. dont think we will even try with this one