The term 'knocked up', today, generally means you're preggers. But back in the 1920s some people actually had jobs as a knocker up. No, they didn't run around impregnating women! Knocker uppers were human alarm clocks who went throughout town knocking on windows to wake up sleeping people so they weren't late for work. You can read about it here.
He's not trying to break in, he just wants to knock you up.
So then, talk around the dinner table, such as, "Did you hear about Jane Smith? She got herself knocked up." would sound perfectly normal and unscathing.
I have to wonder though, who knocked up the knocker ups?