I have one and my doctor knows I have one and she has never said anything bad about it... But I also only use mine like once a week... I don't use it on a daily basis... But even in the instructions it says not to use for a very long period of time...so I'm thinking if you use it excessively it could do more damage then good..

That's why I never purchased one when I was pregnant

I haven't bought one but I know quite a few people that have bought one on this app but I personally bought a app that you can do the same thing and the app was under $10 and I haven't had any issues