That's because null-grav seems to promote funky cellular growth, and transport mechanisms can get a little wonky, too. Since prenatal development is already a balancing act, making babies in space is, for the moment, not recommended.
Sex in space may be dangerous, study says
Human reproduction would not respond well to changes in gravity, according to work performed by a biologist at the University of Montreal. Read this article by Chris Matyszczyk on CNET News.
Awww, no Newtypes?
Hmm. Three or four decades ago, someone (I think it was Larry Niven) wrote a hollowed-out, spinning asteroid for the belt dwellers to have their babies in to avoid developmental problems. Guess I thought we’d already decided space fetuses was a dubious notion.
That would be Confinement Asteroid. (You were right; it’s Niven.)
Ah, good recollection, Jaguar/Avo.