hcg base level and ultrasound

so today according to my LMP I am 5 weeks 1 day. I had an ultrasound at 4 weeks 4 days. they did a baseline test of my hcg which was at 161. they did not have me back to see if it doubled.

ultrasound showed nothing really on abdominal but with a trans vag ultrasound she could see a sac with yoke.

is 161 a good baseline reading for 4 weeks?