Posthumous children or children in the mother's womb, if born alive, are within the foregoing provisions respecting after-born children. Such children shall take any estate or property, real or personal, by descent, transmission, gift, devise, limitation or otherwise in the same manner as if absolutely born at the decease of its parent. If such child is not born alive, the effect shall be the same, to all intents and purposes, as if no such child had ever existed.