Monochorionic twins

Monochorionic twins
Various types of chorionicity and amniosity (how the baby's sac looks) in monozygotic (one egg/identical) twins as a result of when the fertilized egg divides

Monochorionic twins are monozygotic (identical) twins that share the same placenta. If the placenta is shared by more than two twins (see multiple birth), these are monochorionic multiples. Monochorionic twins occur in 0.3% of all pregnancies.[1] 75% of monozygotic twin pregnancies are monochorionic; the remaining 25% are dichorionic diamniotic.[2] If the placenta divides, this takes place after the third day after fertilization.[2]

Contents

Amniocity and zygosity

Monochorionic twins generally have two amniotic sacs (called Monochorionic-Diamniotic "MoDi"), but sometimes, in the case of monoamniotic twins (Monochorionic-Monoamniotic "MoMo"), they also share the same amniotic sac. Monoamniotic twins occur when the split takes place after the ninth day after fertilization.[2] Monoamniotic twins are always monozygotic (identical twins).[3] Monochorionic-Diamniotic twins are almost always monozygotic, with a few exceptions where the blastocysts have fused.[2]

Complications

In addition to a shared placenta, monochorionic twins also have their circulatory systems intermingled in random and unpredictable circulatory anastomoses. This can cause disproportionate blood supply, resulting in twin-to-twin transfusion syndrome (TTTS) in 20%[1] of MoDi pregnancies. This is the main complication of monochorionic twins.

The 80% that of MoDi pregnancies without TTTS still have high rates of birth weight discordance, fetal growth restriction, prematurity and resultant cesarean section deliveries.[1] One twin may also fail to develop a proper heart and become dependent on the pumping activity of the other twin's heart, resulting in twin reversed arterial perfusion.[2] If one twin dies in utero, blood accumulates in that twin's body, causing exsanguination of the remaining twin.[2]

In the case of monochorionic-monoamniotic twins the risk of complications is substantially higher because of additional potential umbilical cord entanglement and compression.[3] However, the perinatal mortality of monochorionic twins is fairly low.[1]

See also

  • twin reversed arterial perfusion

References

  1. ^ a b c d Cordero L, Franco A, Joy SD, O'shaughnessy RW (December 2005). "Monochorionic diamniotic infants without twin-to-twin transfusion syndrome". J Perinatol 25 (12): 753–8. doi:10.1038/sj.jp.7211405. PMID 16281049. 
  2. ^ a b c d e f Shulman, Lee S.; Vugt, John M. G. van (2006). Prenatal medicine. Washington, DC: Taylor & Francis. pp. Page 447. ISBN 0-8247-2844-0. 
  3. ^ a b Pregnancy-Info -- > Monoamniotic Twins Retrieved on July 9, 2009

Wikimedia Foundation. 2010.

Нужна курсовая?

Look at other dictionaries:

  • twins — pl. n. two individuals who are born at the same time and of the same parents. Fraternal (or dizygotic) twins are the result of the simultaneous fertilization of two egg cells; they may be of different sexes and are no more alike than ordinary… …   The new mediacal dictionary

  • monochorial twins — monochorionic twins twins developing with a single chorion; such twins are almost always monozygotic and may be monoamniotic or diamniotic …   Medical dictionary

  • monochorionic — Relating to or having a single chorion; denoting monovular twins. SYN: monochorial. * * * mono·cho·ri·on·ic .män ō .kōr ē än ik also mono·cho·ri·al kōr ē əl adj of twins sharing or developed with a common chorion * * * mono·cho·ri·on·ic… …   Medical dictionary

  • monochorionic — adjective Sharing one foetal membrane, or chorion. Typically used of identical twins …   Wiktionary

  • Monoamniotic twins — Various types of chorionicity and amniosity (how the baby s sac looks) in monozygotic (one egg/identical) twins as a result of when the fertilized egg divides Monoamniotic twins are identical twins that share same amniotic sac within their… …   Wikipedia

  • Conjoined twins — Siamese twins redirects here. For other uses, see Siamese twins (disambiguation). Conjoined twins Classification and external resources A painting of Chang and Eng Bunker, circa 1836 ICD …   Wikipedia

  • diamnionic twins — diamniotic twins twins developing within separate amniotic cavities; such twins may be monochorionic or dichorionic …   Medical dictionary

  • monoamnionic twins — monoamniotic twins twins developing within a single amniotic cavity; they are always monozygotic and monochorionic …   Medical dictionary

  • Twin — Monozygotic ( identical ) twins A twin is one of two offspring produced in the same pregnancy.[1] Twins can either be monozygotic (in common parlance, identical ), meaning that they develop from one zygote that splits and forms two embryos, or… …   Wikipedia

  • Chorion — For the chorion in invertebrate eggs, see Chorion (egg). Chorion Diagram showing earliest observed stage of human embryo …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”