Personally I'm avoiding them, and was concerned about the scans too although decided to go with the two standard ones as I felt the benefits outweighed the risk for me. I do feel that they are a medical tool, and would be concerned about using them too often. They aren't just a microphone. They emit high frequency ultrasound which bounces back and is translated into sound you can hear. For me, I don't want to expose my baby to that for longer than strictly necessary. Obviously, many people use them, and are perfectly comfortable with that decision. It's something you have to research and make your own choices on.