thanks for using health care magic.
At 6 weeks perception of fetal heart beat depends on
the sensitivity of the ultrasound
probe and the experience
of the ultrasonographer. However, since a fetal heart beat
was obtained a week prior to the last ultrasound, there is
a chance that something might be wrong.
There are two possibilities;
1. the situation was misdiagnosed and
2. there is a missed abortion
Whatever the case, you will need to repeat the ultrasound
with a different ultrasonographer or still with your doctor in
a week's time so as to be sure there is no growth nor fetal
heart before drawing conclusions.
Hope this helps you.