Well they did say they were going to a nice place and relax on the beach after it was all over....though I don't think medical science has worked out that the baby making wouldn't work.
crimsonblade said: is it because they look like they could be the baby version of machamp?
Part that, and part the mental image of changing a Krogan's diaper. Human baby poop is bad enough, I don't need weird alien bacteria and bodily fluids to that.