When I had my NT scan they did it the usual way and didnt even mention anything about a vaginal one. I thought they only did it that way if it was really ealy, though they did stress to me the importance of having a full bladder so the scan could be done properly.. maybe if your bladder is not full enough and they cant see baby well they might want to do it vaginally? But then again, i didnt have a fullbladder at all and they did the scan just fine.

any how, hope the scan goes well! I loved seeing our beatiful bubba for the first time! Its just the best.