Higher rates of fetal loss are associated with lower fetal heart
rates; survival is zero at heart
rates below 85 bpm at 6 to 8 weeks of gestation. That said a normal heart rate (110s-160s) by 8 weeks gestation confers a much better prognosis. A repeat sonogram to detect the fetal heart in 3-4 weeks will be helpful.
Best regards,
Dr.