I never heard of this. Often a woman is scheduled for traditional ultrasound with a full bladder. Then you are sent to the restroom to empty your bladder for the TVUS. Fasting alone will not empty the bowels. Laxatives are needed for that. All that would be empty is the stomach. Maybe they think that will help with the TVUS image? I would ask them why. Write back here with their answer because I would love to hear the rationale for this. You are allowed to ask why....so do it!
If they specifically asked you to fast, not just to have a full or empty bladder, my guess would be that they plan to draw a lipid panel or even a glucose tolerance test while you are at your appointment.
to be able to see the baby your bladder has to be completely full or completely empty especially if your not that far along! as far as fasting idk why they would say that unless it had to do with your bowels and making sure there is nothing thats going to interfer with the ultrasound
I've never had to fast for an ultrasound, but I have had to fast for the blood tests that they drew at the same appointment. Call the nurse and ask, if you are not talking about tonight.