Girl Preemies

I'm not sure I could count how many times nurses told us that girl preemies tend to do better than boy preemies. I remember being asked if I knew his gender while in labour and when I told them he was a boy, there were definite looks exchanged. That first afternoon in the NICU I was told by one of the nurses that it was too bad he was a boy as girl preemies usually fair much better. I would then hear this statement at least a few dozen more times over the following few weeks. I'm not sure how it was supposed to be helpful...