Me: "Baby, just to let you know, we'll be doing a rapid DNA test when Jr. is born, just to make sure."

Her: "You bastard! You don't trust me?"

Me: "Of course I do cupcake, but you know hospitals, they switch out kids and screw things up all the time. They always run out of the room with the kids, that's why we're testing your DNA too. I don't want any mistakes."

Her: "But why do we need to test yours?"

Me: "Sweet pea, what if I was weak and cheated on you and knocked some girl up at the same time? And they give you that baby instead? If we only tested me, it would be my kid, not yours, so we test both of us. This is for your own protection to make sure they're not switching babies. That's why we're testing yours too, so we both know we have the right baby."

What kind of monster would want his wife to have to raise some other woman's kid?

It's the only way to be sure she's not getting screwed over.