User blog comment:LuffyPirateKing/Your day with Mane Mane no Mi/@comment-111.235.94.12-20111123000636/@comment-4493594-20111123001743

If he became pregnant as a woman and changed back into a man he wouldn't have a womb anymore... So either the baby would stick in his organs like a tumor or break out of his stomach like that Alien thing if it was big enough.