Space

Well zero-G and/or micro G fluid....mechanics is very much different. It probably more serious for things like bleeding wounds, especially internally. But this can and possibly would also affect pregnancy, or at the least, fertilization.

Also radiation even on a plane is quite a bit higher than most on ground level. There are things that can be done to help shield that. But still, even a constant bombardment at the radiation levels of an "x-ray", could have potentially negative effects.