Just bought a heart monitor. has anyone used one?

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So I've just seen this Angelsounds Baby Sound Monitor Fetal Doppler. I've read through the reviews and although it says should be used from 14weeks onwards. lots of women have been able to use it from as early as 8weeks! I'm currently 11+3. still waiting to have my first scan.Cannot wait for this to arrive so I can try it out myself! I wanted to try it with my last 2 pregnancies but never got round to it. fingers crossed I'll be able to work it properly!