From my experience in Canada, it means impregnate another, but not in a good way. It's usually out of wedlock, unexpected, and maybe not even in a relationship.

From my experience in Canada, it means impregnate another, but not in a good way. It's usually out of wedlock, unexpected, and maybe not even in a relationship. It would seem very out of place for me to hear someone say they knocked up their wife. But common to tell a young girl with a casual boyfriend not to get knocked up.