multiple birth

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Related to Multiple pregnancies: Multiple Births, Multiple gestation

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
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. 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
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 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 ?
26) He also points out that other countries that have financed single embryo transfers have been successful at reducing the rate of multiple pregnancies.
Due to the lack of legal restrictions on the number of transferred embryos or a regulatory body to oversee the work of infertility clinics as well as the possibility of eliminating selected embryos, the number of multiple pregnancies has increased.
We analyzed 19 multiple pregnancies vs 81 singleton pregnancies, matched for gestational age, at a maximum of 5 singleton pregnancies per multiple pregnancy.
Latest figures from the Office for National Statistics show that 49 foetuses from multiple pregnancies - most of them normal and healthy - were destroyed by lethal injection in the womb last year.
Indeed, Pike believes that technology can confer the breast cancer protection that multiple pregnancies provided in the past.
Vitrification has enabled clinics to improve pregnancy rates over those of traditional slow cooling and also to move toward practicing Single Embryo Transfers when possible to reduce multiple pregnancies, and improve lab efficiency.
Fertility rates are also high in Ethiopia, and multiple pregnancies are a possible risk factor for the condition.
The centre also ensures safe individualised care and transfer of embryos is strictly as per the clinical history of the patient so as to reduce the occurrence of multiple pregnancies, she said.
Multiple pregnancies (twins, triplets or more) are very high risk pregnancies where the risks are evident for both mother and babies.
To our knowledge this is the first medical app to compute fetal percentiles and plot fetal growth charts, for singleton and multiple pregnancies.

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