Honestly, I haven't used a fetal doppler myself kasi medyo mahal and ang OB ko naman laging may ultrasound during check-ups, pero a few of my mum friends who bought one swear by Sonoline B or Jumper brands, nakikita nila agad ang heartbeat at lagi silang nag-relax pagkita ng movement. That said, better check with your doctor first which brand they recommend, kasi importante na matuto ka ng proper technique para hindi ka ma-stress kung hindi mo madaling mahanap ang heartbeat (normal yan, lalo na kung beginner ka pa lang!).