BPP Ultrasound

I'm having a Biophysical Profile ultrasound done Friday. I'll be 35+4. My gallbladder has went to crap and we are waiting on my blood work for my Bike Acids, but my OBGYN wants this ultrasound done as well. I'm doing it Friday. I have my regular growth ultrasound Monday. Just wondering if any other mom has had one? What do they look at? What could happen if the ultrasound doesn't look how she wants? I'm a FTM with an angel baby girl and I'm nervous! 🥺