Yes, I have a 3 week old baby boy and I wondered about this as well so I asked his pediatrician and they said that they recommend solely breastfeeding for the nutrients it provides, but it is fine feeding them formula as long as it doesn't cause any issues for the baby. If you choose to use formula you don't want to switch from the kind you have been using without speaking to your baby's pediatrician. I recommend enfamil neuro pro infant formula if you are going to feed your baby formula and still continue to breastfeed. I wouldn't use formula very often though because every time you decide not to breastfeed and/or pump can cause your body to start slowing down your milk production.