Found an amusing article about research into how microgravity affects fertility: http://www.physorg.com/news/2011-01-sex-space-houston-problem.html Basically, it is bad for it in unaugmented organisms. By the time of Eclipse Phase I expect that this side, just like bone loss and lymph buildup, will have been corrected in modern morphs. Still, flats in space are going to need some medical help - any "natural human breeding program" in the Republic will have its work cut out for it. This topic of course leads to another popular topic, sex in space. NASA has the amusing official view that it has never ever occurred on any of their missions (not the slightly more sane "we respect the privacy of our astronauts"), and a fairly high-ranking NASA official I know was told when he asked to stop asking. Russians seem almost as prudish. At a conference on space ethics I attended the question came up, and they happily responded "But the crew are all of the same sex!" At which an ethicist pointed out that that certainty doesn't prevent them from having sex. Upon which the Russian delegation suddenly developed great translation difficulties and couldn't respond to the question :-) Obviously we need more private, and perhaps European, crewed space-flight to get real data. Maybe Big Brother LEO will finally give some answers. From a practical standpoint there are likely plenty of problems. Gravity is a useful placeholder and prevents bodies from drifting apart due to Newtonian mechanics. For the morphologically adventurous maybe remapping erogenous zones to more suitable places is a solution. Or Simspace it is. Actually sleeping in microgravity might be tricky. I expect a hammock-like cocoon might be one nice solution. Air circulation needs to be arranged but not to be too strong.