Honestly, maraming mums use fetal dopplers and the gel is generally safe, it's the same conductive gel they use sa regular ultrasound sa hospital, pero since you're worried, better ask your OB first kung okay lang gamitin mo siya regularly, kasi they know your pregnancy best. One of my mum friends used one throughout and had no issues, pero she still got clearance from her doctor din, and I think that's the smartest approach talaga.