Idiom: to get knocked up – to get (someone) pregnant
Context #1 – At a party with friends
James: I can’t figure out what do bring for my brother’s bachelor party next week.
Candy: Your brother is getting married? I didn’t know.
James: Yeah, he knocked up his girlfriend and they decided to get married.
Candy: Didn’t they date for seven years now. So it’s not really a big deal. They’ve been living together for such a long time anyway.
James: Yeah, we’re all pretty happy about it anyway.
Context #2 – Two friends having lunch
David: How are you feeling these days?
Julie: Well, after I got knocked up I’m feeling pretty strange.
David: Why is that? I’m pretty sure your husband is happy though.
Julie: Oh, we really wanted a child, but my body is having some changes and I’m feeling strange.
Meaning: “(get) knocked up” means to get pregnant. People typically use this as slang and with close friends, family or acquaintances.You would never usually use this term in formal situation, for example with your boss.