Multiple Births
A multiple birth occurs when more than one fetus is carried to term in a single pregnancy. Different names for multiple births are used, depending on the number of offspring. Common multiples are two and three, known as twins and triplets, respectively. These and other multiple births occur to varying degrees in most animal species, although the term is most applicable to placental species.
Multiple birth siblings are either monozygotic or polyzygotic. The former result from a single fertilized egg or zygote splitting into two or more embryos, each carrying the same genetic material (genes). Siblings created from one egg are commonly called identical. Since identical multiples share the same genetic material, they are always the same sex. Polyzygotic (or fraternal) multiples instead result from multiple ova being ripened and released in the same menstrual cycle by a woman's ovaries, which are then fertilized to grow into multiples no more genetically alike than ordinary full siblings, sharing 50% of their genetic material. Multiples called "dizygotic" represent multiples from two eggs specifically. For example, a set of triplets may be composed of identical twins from one egg and a third non-identical sibling from a second egg.
The most common form of multiple births for humans is twins. Many placental species give birth to multiples as a matter of course, with the resulting group called a litter.
Read more about Multiple Births: Terminology, Higher Order Multiples, Human Multiple Births, Cultural Aspects
Famous quotes containing the words multiple and/or births:
“... the generation of the 20’s was truly secular in that it still knew its theology and its varieties of religious experience. We are post-secular, inventing new faiths, without any sense of organizing truths. The truths we accept are so multiple that honesty becomes little more than a strategy by which you manage your tendencies toward duplicity.”
—Ann Douglas (b. 1942)
“As the births of living creatures, at first, are ill-shapen: so are all Innovations, which are the births of time.”
—Francis Bacon (1561–1626)