It is one of the most asked questions in my introduction to astronomy class: can women get pregnant in space? I believe the reason the question is so popular is because there is a lot of confusion surrounding the answer.
Is Pregnancy Possible in Space?
The traditional answer to this question is no. The reason being that there are significant hurdles that stand in the way of a woman becoming pregnant, or at least remaining pregnant once fertilization takes place.
The primary problem with space conception is the effect that radiation can have on both sperm counts and the development of a fetus.
Environments, like that of outer space, that have high levels of radiation can be harmful to the creation of sperm in males. With lower sperm counts, the likelihood of pregnancy in the first place is diminished.
But even if conception occurs, the exposure of radiation to a forming fetus would kill the cells almost immediately. So even if fertilization could occur, the cells would not be able to replicate and form an actual fetus.
A third problem exists, and that is the extremely low gravity environment of space. While the exact effects have not been studied in detail, it is known that a gravity environment is needed for proper bone development and growth.
This is why astronauts have to exercise in space regularly in order to prevent muscle atrophy and loss of bone mass. It is also because of this that astronauts that return to Earth after long stays in space (like aboard the International Space Station) can require re-acclimation to Earth's gravity environment.
So it seems that even if the radiation problem could be overcome, there is still a distinct need for gravity for proper physiological development.
Overcoming the Radiation Problem
If man is to venture out into space on a more permanent basis (like extended trips to Mars) these problems will need to be overcome. But how?
The radiation problem is the big one, and it is one that NASA is actively dealing with, though not primarily for the pregnancy issue.
Astronauts taking extended trips into space, like the proposed multi-year jaunts to Mars, would be exposed to much higher levels of radiation than astronauts have ever faced before. Current space ship designs can not provide the necessary shielding to provide the needed protection to avoid development of cancers and radiation sickness.
And it is not just a problem while traveling to other planets. Due to the thin atmosphere and weak magnetic field of Mars, the astronauts would still be exposed to harmful radiation on the surface of the red planet.
So if permanent residencies are ever going to exist on Mars, like those proposed in NASA's hundred-year starship, then better shielding technology would have to be developed.
Since NASA is already thinking of solutions to these problems, it seems possible that we could one day overcome the radiation problem.
Overcoming the Gravity Problem
Strangely, at least in my mind, the problem of a gravity environment may be more difficult to overcome.
There are some spacecraft designs in the pipeline, like the Nautilus-X, that employ "artificial gravity" designs - specifically centrifuges - that would allow for at least a partial gravity environment on part of the ship.
The problem with such designs is that they can't yet replicate a full gravity environment, and even then occupants would be constrained to one part of the ship. This would be difficult to manage.
Further exacerbating the problem is fact that the spacecraft needs to land. So what do you do once on the ground?
Ultimately, I believe the long-term solution to the problem is the development of anti-gravity technology. Such devices are still a long way off, partially because we still don't fully grasp the nature of gravity, or how gravity "information" is exchanged and manipulated.
However, if we could somehow manipulate gravity it could be possible to create the necessary environment to allow a fetus to develop. Though overcoming these obstacles is still a long way off.