Is yoga safe in first trimester?

Hey ladies. Just wondering if there are any yoga instructors or yoga practicing mummas who can advise. I'm 5 weeks pregnant following IVF and haven't been able to practice for the past month or so whilst I've been on stims/ getting my ovaries messed with for egg collection...

I'm feeling good so far and I'm really ready to do some super gentle yoga to help clear my head ( feeling v anxious at this early stage). I had understood that easy restorative yoga was safe -as long as I follow pregnancy adjustments and don't twist. BUT I just got turned away from a class. The teacher said they don't recommend yoga until second trimester and they wouldn't be covered to teach me.

Obviously don't want to put the bean at risk, but I want to take a sensible view on this. I'm not talking about hard core bikram sweaty yoga- just super gentle stretching and breathing. Anyone been in this position or taught ladies like me? Thanks!