Helen, I don't think I have seen you scan pic? have you got a link to where it was posted?
Adele, I guessed girl for you, just a hunch based on baby shape , head shape, etc, from having scans with my others! mind you a 50:50 chance. I have no idea about this nub thing!!
What do you two think you are having?
Old Wifes Tales - Normally you can tell from looking at the pregnant lady's bump shape, better if she is wearing tight clothes and can be decieving if very tall , short or round mum before pregnancy. Better to guess once the mum is at least half way onwards for better guess.
BABY BOY - Bump all out front and low, like a non pregnant lady has tripped over and fallen onto a bowling ball and when she gets up it's stuck on the front still! (you can't tell if they are prnegnant from the back they look normal).
BABY GIRL - Bump all round her middle , much higher bumps, (where guessing gets tricky with tall or short ladys), and the lady will have put on some love handles or weigh all round the sides. (you can therfore tell from the back that she is pregnant).
Some swear that the reverse happens for them, so once you have had one, you can ususally tell the difference and how you carry, to guess what you next one is.