Identical Twins No Heartbeats 6 Weeks Ultrasound

My husband and I had first ultrasound at what I thought was 7 weeks. The nurse who did the ultrasound said she couldn't give us any results until a radiologist or doctor looked at the results. But, at the end she showed us twins, but no heartbeats.

We weren't worried since she didn't say it was a problem and she showed us the twins. Then, 2 days later, got the call from the doctor and he told us of the possibility of fetal demise since no heartbeats.

I'm having blood work done to check HCG levels in 48 hour span and a 2nd ultrasound is scheduled next week. Also, told these look like identical twins (I am an identical twin as well). Is it possible since the twins are identical, that they're smaller and heartbeats just aren't visible yet?