multiple birth

(redirected from octuplet)
Also found in: Dictionary, Medical, Wikipedia.

multiple birth,

bringing forth of more than one offspring at birth. Although many smaller mammals bear several young at a time, multiple births are relatively uncommon in humans and other primates. Twinning, the process that leads to the production of more than one offspring, results in twins, and with decreasing frequency, triplets, quadruplets, quintuplets, sextuplets, septuplets, and octuplets.

In the one-egg, or identical, type of twinning, a single fertilized ovum divides to form two complete organisms. Such twins are always of the same sex, are usually extraordinarily similar in physical appearance, and have identical blood-group types. Twinning to form one-egg identical twins usually takes place early in pregnancy. If considerable development has taken place before the twinning occurs, there may be an incomplete separation of the two embryos resulting in conjoined twinsconjoined twins,
congenitally united organisms that are complete or nearly complete individuals, historically known as Siamese twins. They develop from a single fertilized ovum that has divided imperfectly; complete division would produce identical twins, having the same sex and
..... Click the link for more information.
. Despite their similarities, identical twins have epigenetic differences that influence how their common DNA is used and expressed.

Fraternal twins, which are more common than identical twins, are those that develop from two separate ova, each fertilized by a sperm. Fraternal twins may or may not be of the same sex and need not resemble each other more than do any other two offspring of the same parents. In the United States twins occur once in approximately 40 births. In rare cases, non-identical embryos can fuse in the womb to produce a condition called chimerism, in which some of the individual's cells come from one of the embryos and the rest of the cells come from the other, genetically distinct embryo.

The incidence of multiple-egg births is in part genetically determined, varying according to race and family tendencies; and it is also influenced by external factors, i.e., the incidence increases with increasing age of the mother and the number of children she has already borne. One-egg, or identical, twinning occurs with the same frequency in all women, regardless of race, age, or other factors. There is evidence from comparative biology that deleterious factors in the environment of the newly fertilized ovum, such as a reduction in oxygen, increase the likelihood of one-egg twinning. Fertility drugsfertility drug,
any of a variety of substances used to increase the possibility of conception and successful pregnancy. Different methods are used to correct or circumvent the many different functional disorders of both males and females that can interfere with conception and
..... Click the link for more information.
 such as clomiphene, which are used when the cause of infertility is lack of released ova, sometimes cause several ova to be released and fertilized simultaneously. The use of these drugs has led to a rise in the incidence of multiple births, including sextuplets, septuplets, and octuplets.

References in periodicals archive ?
The successful delivery of America's second set of octuplets on January 26, 2009, brings an entirely new meaning to the phrase, "It takes a village to raise a child.
Given prior coverage of similar events, the octuplet birth is a new entry into the record books and a story of human survival.
Baby Rade is Mandy and Paul's third child since the death of their octuplets which catapulted the shy girl from Balsall Common into the national limelight.
Word about the octuplets didn't emerge until tips were called in to news organizations Sunday.
Nadya Suleman already had six children when she gave birth to the world's first surviving octuplets.
The octuplets, who were born in January, are still in hospital and it is not clear when they will leave.
Nadya has been hiding away in the rundown property with her ten sons and four daughters, including the octuplets who earned her the Octomum nickname when they were born in January 2009.
The Suleman octuplets, born in California in January 2009, are the longest-living octuplets in known history.
In 2009 she outraged America by giving birth to octuplets through IVF despite having six other children and no job.
She was quickly known as "Octomom" and her octuplets became the longest surviving octuplets in the world.
After triplets come sixteenths (four syllables per beat), sextuplets, then octuplets (thirty-second notes).