Congrats first of all:)!!!! I can't really answer your question. I have researched miscarriages a lot lately as I just passed everything from my first pregnancy. We saw a heartbeat at 6 weeks, but didn't have one at 7w3d. From what I have read, the 6-8 week mark seems to be when most miscarriages happen. However, when reading all of the forums, it seems miscarriages happen all over the board. I wish you a healthy baby. I do believe your risk is really low now.
Once you hit the 10 week mark with a heartbeat the risk drops dramatically. Congrats!