1. Using the threat of killing someone's baby (or threat of impregnating someone so that you can kill the baby) to try and convince them to do something.
2. Using dead baby/abortion jokes as an opening line for a persuasive speech or argument.
1. A - Guy 1: Give me a bite of that candy bar before I kill your baby. Guy2: Don't try your abortion-coercion on me!
1. B - If you don't get over here I swear, I'll knock you up and kill the baby!
2. - Politician: Before I tell you why we should ban abortion, I've got a joke for you all this evening. How many babies does it take to paint a barn...