I am 5 weeks and 5 days pregnant. As far as the ultrasounds goes, we heard a heartbeat and then the tec was looking around and saw either a blood filled sac outside of the gestational sac or a second gestational sac. My first question is, do twins develop at the same rate, for instance, could Twin A have a heart beat already and Twin B not have a heart beat at this point, but still developing fine? Second, if it s a blood filled sac, what does that mean for the pregnancy? I go back to the OB for another ultrasound on Tuesday, today is Friday, to check again to see if we can see what is going on. The tech said she couldn t be sure what the sac was (a baby or blood) at the point of the ultrasound.