A multiple birth is the culmination of one multiple pregnancy, wherein the mother delivers two or more offspring, one for each fetus. A term most applicable to placental species, multiple births occur in most kinds of mammals, with varying frequencies. Such births are often named also according to the number of offspring, as in twins and triplets. In non-humans, the whole group may also be referred to as a litter, and multiple births may be more common than single births. Multiple births in humans are the exception, and can be exceptionally rare in the largest mammals.