An underappreciated challenge of interstellar travel:
If the human race ever travel to other star systems, the journey could take generations. … With ideas such as light-speed travel or 'suspended animation' still a glint in a science fiction writer's eye, reproduction in space might be essential … But scientists are not sure it is even possible. 'Giving birth in zero gravity is going to be hell because gravity helps you,' said biologist Athena Andreadis of the University of Massachussetts, 'You rely on the weight of the baby. Sex is very difficult in zero gravity, because you have no traction and you keep bumping against the walls.'
The Dish 