When he and his wife come home, the milkman is dead on the floor.

There were about 20 people present when the joke was tole and, when polled, we gave the reasons stated.

Ah! So the division of laughter among the sexes goes from this-- the women are amused by the idea labour pains would kill a man ("They're such babies") and the men laugh because of the father not recognizing fromt he lack of pain he's a cuckold.