twin (twin) one of two offspring produced in the same pregnancy and developed from one oocyte (monozygotic) or from two oocytes (dizygotic) fertilized at the same time. 
twin
twin [twin]
twin
Patient discussion about twin.
)
Twins. (A), The most common type of monozygotic twinning, with division of the inner cell mass of the blastocyst resulting in separate amnions but a single chorion and placenta; (B), a rare form of monozygotic twinning, with complete division of the embryonic disc resulting in two embryos in a single amniotic sac with a single placenta and chorionic sac; (C), monozygotic twinning with division occurring between the two-cell and morula stages to produce identical blastocysts, resulting in separate amniotic and chorionic sacs and either separate (shown) or fused placentas; (D,E), dizygotic twinning, with (D) or without (E) fusion of the placenta and chorion.
allantoidoangiopagous twins twins united by the umbilical vessels only.
conjoined twins monozygotic twins whose bodies are joined to a varying extent.
diamniotic twins twins developing within separate amniotic cavities; they may be monochorionic or dichorionic.
dichorionic twins twins having distinct chorions, including monozygotic twins separated within 72 hours of fertilization and all dizygotic twins.
dizygotic twins , fraternal twins, heterologous twins twins developed from two separate oocytes fertilized at the same time.
identical twins monozygotic t's.
impacted twins twins so situated during delivery that the pressure of one against the other prevents simultaneous engagement of both.
monoamniotic twins twins developing within a single amniotic cavity; they are always monozygotic and monochorionic.
monochorionic twins twins developing with a single chorion; they are always monozygotic and may be monoamniotic or diamniotic.
monozygotic twins two individuals developed from one fertilized oocyte; they have identical genomes.
omphaloangiopagous twins allantoidoangiopagous t's.
Siamese twins conjoined t's.
similar twins monozygotic t's.
twin (tw n)n. One of two offspring born at the same birth. adj. 1. Being two or one of two offspring born at the same birth. 2. Consisting of two identical or similar parts; double. |
twin
Etymology: AS, twinn, double
either of two offspring born of the same pregnancy and developed from either a single ovum or from two ova that were released from the ovary simultaneously and fertilized at the same time. The incidence of twin births is approximately 1 in 80 pregnancies. Kinds of twins include conjoined twins, dizygotic twins, interlocked twins, monozygotic twins, Siamese twins, and unequal twins. See also Hellin's law.
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.
twin
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.
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...
you're great...
Q. How do I know whether I will get twins or not? Twins have always fascinated me and I cannot wait to get pregnant and have twins. My husband has already bought identical dresses hoping that we will be expecting twins shortly. As I am conceived now that I am pregnant, I am going for a test tomorrow. How do I know whether I will get twins or not?
A. do you have identical twins in your family? if so the chances of you having twins is greater, anyway, checking it out can be done only by ultrasound screening. only then they can see if there are two heartbeats and see two fetuses.
Read more or ask a question about twinWant to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit the webmaster's page for free fun content.
| ?Page tools | ||
|---|---|---|
|