If I remember correctly, many schools offer direct entry masters programs for either CNMs or WHNPs without having any nursing experience. The programs are usually 3 years long and you get you BSN the first year and your MSN the last 2 years. If you are already an RN, they also offer programs like this, but I know less about them. You already have to have a bachelor's degree in something else to get into these programs unless you are an RN.
It might be difficult to practice at first without much experience, but everyone has learning to do at any new job no matter what degrees you have.