Hello, good day!

I'm at approximately 11 weeks of my pregnancy. But we're not sure though because my menstruation was irregular. My OB tried to find the baby's heartbeat by using Doppler, but can't seem to find one. So she scheduled me for a TVS. Can I ask if is it possible to not determine baby's heartbeat at the 11th week of pregnancy via Doppler, and is it safe to have a TVS at early stage of pregnancy.