1st ultrasound measurement

I want to know if my baby measuring 6dayd behind at the 7week ultrasound should have been a red flag, or the fact that the heart beat was high at 188. I lost the baby at 11weeks to a MMC baby only measured 9w3d 
My question is for those of you that had a mc after 7 weeks and were able to hear baby's HB at first ultrasound, were there any red flags? Did your baby measure correctly or did your due dates get pushed back like mine?