nub theory?? what?

[bippitybopityboo]

I have seen lots of people posting about a num theory? I'm very confused as to what it actually is? I have zoomed in on what I think is the nub on my 12 week scan. From what I have read I think it's a girl but I don't think I understand the theory correctly

If you google Nub theory there's quite a bit of info and pics explaining it. It really depends on how clear your scan pic is. Congrats!