There are a few factors that can cause it - that the first born is a girl, breech, prem, or family history. DD's only known thing was that she is a girl, so a bit sucky! The other added bonus is for her, that when she has a baby, she has a higher chance of her baby having it too.

So for me, I guess, I just have to keep my fingers crossed that if I have another, it won't happen again.