“Giving birth in zero gravity is going to be hell because gravity helps you” on the ground, Andreadis told Space.com. “You rely on the weight of the baby.”

And that’s if would-be parents can even get that far.

“Sex is very difficult in zero gravity, apparently, because you have no traction and you keep bumping against the walls,” Andreadis said. “Think about it: You have no friction, you have no resistance.”

Ultimately, even if human babies can successfully be conceived and born in space, multigenerational space travel comes with a host of other difficulties. In addition to the ill effects of microgravity on the body, people on such a journey could fall prey to disease, and the psychological effects of being stuck onboard a vehicle in the vacuum of space could take their toll.