Many mothers who breastfeed but also want or need to use baby formula on occasion, fear it will cause their babies to have nipple confusion.
This is why some mothers who breastfeed never consider using formula. Not because they are against formula - but because they are afraid their babies will not know what to do when a different type of nipple is introduced.
This is an old myth and is not true. Babies don’t end up having nipple confusion even when using both natural and artificial nipples. What they do have is nipple preferences which simply takes a little experimenting to find the type of artificial nipple your baby prefers.