text: Seahorses can't technically *get* pregnant, although they can carry the unborn baby seahorses in a pouch, so it is sort of like being pregnant, I guess.\n\nBut the main reason that human men can't do it is that we are mammals, not sea animals.  In mammals, whether it is dogs, cats, gorillas, sheep, tigers, or humans, one characteristic is that the babies grow in a placenta inside the female.