multiple birth

(redirected from Multiple gestation)
Also found in: Dictionary, Thesaurus, Medical, Legal.
Related to Multiple gestation: polyhydramnios, Multiple pregnancies

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 ?
Many health plans have seen the same trends in multiple gestations among their members.
Among women in whom fetal heart rates could be identified, rates of multiple gestations were not significantly different in those who received letrozole (9 of 67 women, or 13%) and those who got clomiphene (8 of 85 women, or 9%), according to the researchers.
In the case of a multiple gestation an added distress would arise because of the necessity of somehow choosing which infant(s) to keep and which to give up.
Thus, it may reduce the number of false negatives and increase the confidence in the results for multiple gestation pregnancies.
SET has been advocated to eliminate multiple gestation, but previous studies have demonstrated inferior delivery rates due to a limited ability to predict a given embryo's reproductive potential.
Pacific Fertility Center has been taking steps to minimize the risk of multiple gestation for several years.
The rationale for moving to aromatase inhibitors is that this class of drugs is thought to have fewer antiestrogenic side effects, including a lower risk of ovarian hyperstimulation syndrome and a lower risk of multiple gestation.
However, this has come with a marked increase in multiple gestations that often lead to profound health risks, emotional burdens and financial consequences for families and businesses.
And in a 2012 joint committee opinion, ACOG and SMFM said that cell-free DNA testing should not be offered to low-risk women or women with multiple gestations because it hadn't been sufficiently studied.
The main advantage of expectant management is avoiding multiple gestations which are accompanied with obstetric and prenatal complications, postnatal disability and the considerable burden on healthcare system can not be neglected in this regard.
Women need to understand that transfer of more embryos can result into multiple pregnancies and multiple gestations are associated with numerous complications such as increased risk of pre-eclampsia and development of gestational diabetes.
Aided by contributors who work in obstetrics and gynecology and sonography in the US, she reviews aspects of ultrasound in general, then discusses ultrasound scans as related to pelvic anatomy and physiology, anomalies, and gynecological pathology; each trimester of pregnancy; the placenta and umbilical cord; the cervix during pregnancy; anomalies associated with polyhydramnios and oligohydramnios; multiple gestations and their complications; maternal disorders and pregnancy; fetal syndromes; Doppler applications; infertility; volume sonography; invasive procedures; and the sonographer's role in the grieving process.

Full browser ?