You misunderstood me twice, my brother in fetishes.
Firstly, I am too a impregnation enjoyer, I just like also the pregnancy that follows and even the childcare after, if the game allows (not our case here).
Secondly, I said that we could get impregnation in the game. The way I would do if I was the writer would be something like:
Deryl: "Hey bro, I just made a fertility serum. Inject this and every girl you fuck will get pregnant."
MC: "How did you do this?"
Deryl: "You got Angelina pregnant, so we isolated the mutation that allowed her to get knocked up and replicated in the serum"
MC: "Cool" Proceeds to make an orgy with the harem*