I am wondering why at 16 weeks that I would have a miscarriage? I am 46 and we used donor eggs (she was 23), Everything was going along great, I went in at 16 weeks for an ultrasound and everthing was fine. The baby was measuring fine and the heart beat was great. We went in for the level 2 US at 18 weeks and their was no heartbeat, the baby was measuring at 16 weeks. I did not have any bleeding, cramping, nothing. The only thing that was wrong was that I got sick and my doctor prescribed me Tamaflu and Z-pak for a sinus infection. My doctor has no clue what happened, they are going to do some tests on the baby to see if there were some abnormalities.