There is documented evidence that some astronauts have had sex on the International Space Station. I mean, who wouldn't want to try?
As far as an actual pregnancy goes, our bodies have evolved below 1g. Sperm are highly mobile and will swim up against the gravity gradient to reach the egg.
But what do they do in the absence of a gravity gradient? And, more to the point, if one is successful, the complex development of the embryo will almost certainly be affected by the absence of a gravity gradient as it develops.
Does a developing embryo need to have a defined 'up and down' in order to develop properly?
A 2009 study conducted in simulated zero gravity, and another conducted in 1996 in which NASA scientists sent embryos into space, did not see any mammalian embryos develop.
However, China sent a microgravity satellite, SJ-10, with 6,000 mouse embryos.
Within four days, the space embryos developed into a normal-looking blastocyst, which are more complex embryos that demonstrate the onset of cell differentiation. Of course, a blastocyst is a long way from an adult mouse, so the verdict is still out.
