I get my girls pregnant (not inseminated) even they use anti-preg. I started a new game, hired 4 slaves, put them training on day and working in the brothel at night. Then I just hired 3 gangs, 2 sabotaging and 1 acquiring territory. When I clicked "next week >>", one got knocked up. in one game, I had about 500 cash before changing week, in other game about 100 cash.
I never pressed "girl details..."-button before changing the week. Maybe that is the reason?
Also, once I got girl from event; customer did not pay, and gave his daughter automatically as payment (i did not have to ask about it). When she was in dungeon, I pressed "girl detail..." button in dungeon (that was the first time in that game when I pressed that button), took off anti-preg, and tried to make her pregnant. I did not succeed, but when I changed week, 2 of my slaves got pregnant by customers (even they had anti-preg on, when I checked it later)
I have lurked in the forum some time, but decided to post this, since I did not see this one mentioned in this thread. Downloaded r450, updated it to r452, no girl editors or such used.