As just mentioned DH and I didnt want to find out the sex of Hendy until his birth and we didnt officially. But i had to have a further scan at 28 weeks as Hendy was measuring big and while i didnt see anything (as i was lying on my side facing away from the screen, cause he was too heavy to lie on my back) DH was really upset as he was sure that he saw a penis, and even though it was a suprise at the birth DH was right, our son had obviously flashed himself!!

Maybe you could call prior to the scan and explain your predicament, im sure they deal with this sort of thing all the time!