Okay, just come back to this. What I said was one professional sonographer's opinion. She also seemed to be of the opinion that ultrasounds should only be done out of medical necessity (and you can argue that a reassurance scan is of medical necessity if it helps relieve the stress the woman is experiencing). When I saw my tiny 8 week old embryo on the screen, with just a few flickering cells representing the heart, I felt an intense sense of intruding on something that was so incredibly private - my baby in the very first stages of development. It was something that I wasn't 'meant' to see. When the sonographer said that although we could see the heart beat, she didn't want to listen to it as it may upset the baby, it completely changed the way I looked at scans.
I know how stressful a pregnancy is when you had previous miscarriages, I've experienced that myself. Scans and hearing the baby's heartbeat do help reassure you, and I agree that is important. But I can't help but feel that we just simply don't know enough about the effects of dopplers at such a vulnerable stage of pregnancy, and the chances are they will add to the stress of the mother if she can't find the heartbeat.
Like I said, even at 15 weeks, the student doctor couldn't find the baby's heartbeat. She found mine, which was very high (115 I seem to remember), as I was getting quite stressed out that no heart beat was being found. Then the baby kicked the doppler, and the doctor found the heart beat.