twin
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twin
[twin]one of two offspring produced in the same pregnancy; twins occur about once in every 86 births.
Dizygotic or fraternal twins develop from two separate ova fertilized at the same time. They may be of the same sex or of opposite sexes, and are no more similar than any other two children of the same parents. Called also binovular, dichorial, dissimilar, and unlike twins.
Monozygotic or identical twins develop from a single ovum that divides after fertilization. (See illustration at monozygotic.) Because they share the same set of chromosomes, they are always of the same sex, and are remarkably similar in hair color, finger and palm prints, teeth, and other respects. Monozygotic twins have exactly the same blood type and can accept tissue or organ transplants from each other. Called also enzygotic, monochorial, mono-ovular, similar, or true twins.
Approximately one third of all twins are identical and two thirds are fraternal. It is not clearly understood exactly what causes a single ovum to divide shortly after conception and thereby produce identical twins, although it seems to be a chance occurrence. The reasons for the production and fertilization of two separate ova that result in fraternal twins are not well understood either, but it is thought that a tendency toward fraternal twins runs in families and is transmitted through the genes of the mother. Women are more likely to have fraternal twins in their later childbearing years, between the ages of 30 and 38 years, than earlier. Older age in the father also seems to be a factor with fraternal twins.
Dizygotic or fraternal twins develop from two separate ova fertilized at the same time. They may be of the same sex or of opposite sexes, and are no more similar than any other two children of the same parents. Called also binovular, dichorial, dissimilar, and unlike twins.
Monozygotic or identical twins develop from a single ovum that divides after fertilization. (See illustration at monozygotic.) Because they share the same set of chromosomes, they are always of the same sex, and are remarkably similar in hair color, finger and palm prints, teeth, and other respects. Monozygotic twins have exactly the same blood type and can accept tissue or organ transplants from each other. Called also enzygotic, monochorial, mono-ovular, similar, or true twins.
Approximately one third of all twins are identical and two thirds are fraternal. It is not clearly understood exactly what causes a single ovum to divide shortly after conception and thereby produce identical twins, although it seems to be a chance occurrence. The reasons for the production and fertilization of two separate ova that result in fraternal twins are not well understood either, but it is thought that a tendency toward fraternal twins runs in families and is transmitted through the genes of the mother. Women are more likely to have fraternal twins in their later childbearing years, between the ages of 30 and 38 years, than earlier. Older age in the father also seems to be a factor with fraternal twins.
conjoined t's Siamese twins.
dizygotic t's (fraternal t's) twins that develop from two separate ova fertilized at the same time; see twin.
identical t's twins that develop from a single ovum; called also monovular or monozygotic twins. See twin.
impacted t's twins so situated during delivery that pressure of one against the other produces simultaneous engagement of both.
mono-ovular t's (monovular t's) (monozygotic t's) identical twins.
Siamese t's monozygotic twins whose bodies are joined; see also siamese twins.
unequal t's conjoined twins (Siamese twins) of which one is incompletely developed.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.
twin
(twin),1. One of two children or animals born at one birth.
2. Double; growing in pairs. May be monozygotic or dizygotic.
[A.S. getwin, double]
Farlex Partner Medical Dictionary © Farlex 2012
twin
(twĭn)n.
One of two offspring born at the same birth.
adj.
Being two or one of two offspring born at the same birth: twin sisters.
v. twinned, twinning, twins
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.
twin
One of 2 gestational products that develop during a single intrauterine gestational period. See Dizygotic twin, Monozygous twin, Higher multiples, Partial twin, Siamese twin, Vanishing twin. Cf Siamese twins.McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.
twin
(twin)1. One of two children born at one birth.
2. Double; growing in pairs.
[A.S. getwin, double]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012
twin
(twin)1. One of two children born at a single birth. May be monozygotic or dizygotic.
2. Double; growing in pairs.
[A.S. getwin, double]
Medical Dictionary for the Dental Professions © Farlex 2012
Patient discussion about twin
Q. anything a mother should know about the last period of twin pregnancy? she is in her 7th month and starting to be real heavy... her legs hurt like crazy. anything to help her with?
A. thanks for all the information! I hope everything will go on well...
Q. Is there a bigger risk of autism for the newborn in twin pregnancy?
A. thanks Dominicus!
you're great...
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