I think it's a sort of "I'm happy you're happy" thing. Whenever I congratulate someone on having a child, I'm not literally congratulating them on having sex an

I think it's a sort of "I'm happy you're happy" thing. Whenever I congratulate someone on having a child, I'm not literally congratulating them on having sex and spawning another human. That would be silly. Although, there are many couples who can't get pregnant who would like to, so in cases like that, maybe literal congratulations would be in order?