Large mammals which give birth to twins is much more rare, but it does occur occasionally even for mammals as large as elephants. This separates from the wall of the uterus during labor and the fetus works its way towards the birth canal. In these animals, each fetus is surrounded by its own amniotic sac and has a separate placenta. Most smaller mammals have multiple births, producing litters of young which may number twelve or more. The mother encourages the newborn calf to rise to the surface of the water to breathe. In the case of whales, dolphins and porpoises, the single calf is normally born tail first which minimizes the risk of drowning.

This means that it is born in a more advanced state than a human baby and is able to stand, walk and run (or swim in the case of an aquatic mammal) shortly after birth. In these large animals, the birth process is similar to that of a human, though in most the offspring is precocial. Large mammals, such as primates, cattle, horses, some antelopes, giraffes, hippopotamuses, rhinoceroses, elephants, seals, whales, dolphins, and porpoises, generally are pregnant with one offspring at a time, although they may have twin or multiple births on occasion. Some of these are ovoviviparous, with the eggs being hatched inside the mother's body, and others are viviparous, with the embryo developing inside their body, as in the case of mammals.

Some reptiles, amphibians, fish and invertebrates carry their developing young inside them. In marsupials, the fetus is born at a very immature stage after a short gestation and develops further in its mother's womb pouch. In some species, the offspring is precocial and can move around almost immediately after birth but in others, it is altricial and completely dependent on parenting. In mammals, the process is initiated by hormones which cause the muscular walls of the uterus to contract, expelling the fetus at a developmental stage when it is ready to feed and breathe. Lambing: the mother licks the first lamb while giving birth to the secondīirth is the act or process of bearing or bringing forth offspring, also referred to in technical contexts as parturition. For the Star Trek episode, see Parturition (Star Trek: Voyager).

Mom and baby elephant outline