I can't see a nub so my boy guess a based on skull. I think boys have slightly bigger foreheads. Not that I'm saying your baby has a big head lol. I posted my boy and girl scan pics side by side in the pregnancy forum, thread is near bottoms of page 1 and called ,please compare my 2 scan pics and give me a guess. If you look at that I think the difference is quite obvious. When do you find out lovely? Xx