6 week ultrasound question

I’m wondering if it’s normal to not see a yolk sac, or anything else other than the gestation sac at 6 weeks? I had an abdominal ultrasound (to rule out ectopic pregnancy) after I had a drop of spotting, it freaked me out since I’ve had 2 past ectopics and a tube removal.

My HCG is increasing normally and is fitting for how far along I am, however during the abdominal ultrasound the doctor mentioned how they couldn’t see a yolk sac, embryo, etc. They’re having me come in for a transvaginal scan next week to make sure there is one.

Is it normal not to see one on an abdominal scan this early?