I know you said this 13wk ultrasound is because you've had two previous miscarriages (for which I am very sorry to hear), but what is the purpose of it? Why can't you transfer care to the BC without this ultrasound? What difference would this u/s make?
You should be able to hear a heartbeat with a doppler at 13wks if you want.
If you are going to have another miscarriage, having this ultrasound is not going to prevent that. All an u/s tells you is that the baby is doing fine at that particular moment in time and things could change just hours later.
If it were me, not that you asked, I would cancel this 13wk ultrasound and have the 20 week evaluation if I needed reassurance. They will be able to see a lot more of baby at 20wks than at 13.
It would make me feel uncomfortable to have that many ultrasounds. Plus, doppler also uses ultrasound technology so in addition to transvaginal and transabdominal u/s, you are being exposed to u/s every time a doppler is used as well. Add all of that up and it can be substantial...add constant electronic fetal monitoring in the hospital and another late pg u/s to the mix and we're talking hours of u/s exposure.
There was a study released just a week or so ago about exposure to u/s.
http://www.wtopnews.com/?nid=106&pid...=873576&page=2
Here's some more general info on ultrasound
http://www.plus-size-pregnancy.org/P...oundsafety.htm
I'm not saying all u/s is bad, but I'm not convinced it is completely safe either. We all have our comfort zones. Good for you for thinking this through.