Actually both men and women can get pregnant with Aliens. To make it easier for your sims to get abducted hold down the ctrl+ shift+ c to get the cheat box up and type in boolprop testingcheatsenabled true then press enter, once you've done that right click on the telescope it'll say something along the lines of debug- get abducted by aliens, wether you have a male or female sim being abducted they will have a chance of getting pregnant. To make it even easier; when you have the boolprop cheat on, right click on any gender of sim (the one you want pregnant) and click on spawn... then click on tombstone of L and D. A tombstone will appear, click on the tombstone and you'll get many options click on the option more... then click on get me alien pregnant, and your sim will get pregnant. Also with the tombstone of L and D you can speed up pregnancies, so that way there you can have your sim have their child in one day.