At home Doppler

I've seen several post of lady's that have one so I was looking into buying one and ran across on the net your not supposed to use them often and if you do it could cause hearing issues infertility issues in the baby list goes on.. before I make my decision I'd like to hear opinions on what y'all think are they worth the risk? Or is using them completely safe? I know they use them at the dr but it's once a month not every day.