I have two different files, one that was specifically geared to get abductions (Scientist with the aspiration of nerd brain so there was a rocket). He went to Sixam, had the satelitte and the wormhole generator... He got abducted twice. First time, no pregnancy. Second time, there was... but then the game crashed. And of course, the last save was JUST before the pregnancy... after trying and trying and trying to get him abducted again (which he never did), he did meet a female alien that he moved in and tried for baby with, but still no alien pregnancy. I think the best solution would be to up the chance of pregnancy but either a button to turn things off, OR the ability to cancel the interaction if one doesn't want alien pregnancy or abduction. I don't want alien babies all over the place, but I just want one or two!
I even have a second file that I was trying with and no abductions at all for him.