I have yet to see a sim get impregnated after an alien abduction. One sim was abducted 9 times, never impregnated. I've been trying with another, got to 8 times and then tried installing the MCC Command Center and changed the pregnancy rate for young adults and adults to be 100 percent, restarted the game and 2 more times, nothing. I give up, going to have to use MCC Command Center to just start the pregnancy.
I can confirm from my gameplay that yes, it's possible.
It's not super likely--you might need to SEARCH FOR THE TRUTH a lot--but if you have an alien in your household you're super likely to get abducted and perhaps impregnated.
