Birth is the process in animals by which an offspring is expelled from the body of its mother. Different forms of birth are ovipary, vivipary or ovovivipary. In humans, the unborn offspring is called fetus after its embryonary stage. Birth - Medical meanings. Childbirth is the process at the end of a successful human pregnancy that results in a baby being born. Natural childbirth is the technique of minimizing medical intervention, particularly anaesthetics, during childbirth.