| Conjoined twins | |
|---|---|
| Other names | Siamese twins, monstra duplicia |
 | |
| X-ray of conjoined twins, Cephalothoracopagus. | |
| Specialty | Medical genetics  |
| Symptoms | Bodies fused |
| Complications | Depends on type |
| Usual onset | Beginning of pregnancy |
| Duration | Lifelong |
| Types | see article |
| Causes | Incomplete fission |
| Treatment | Surgery, symptomatic care |
| Prognosis | Depends on type; occasionally may survive |
Conjoined twins, popularly referred to as Siamese twins,[1][2] are twins joined in utero.[a] It is a very rare phenomenon, estimated to occur in anywhere between one in 49,000 births to one in 189,000 births, with a somewhat higher incidence in Southwest Asia and Africa.[5] Approximately half are stillborn, and an additional one-third die within 24 hours. Most live births are female, with a ratio of 3:1.[5][6]
Two possible explanations of the cause of conjoined twins have been proposed. The one that is generally accepted is fission, in which the fertilized egg splits partially.[7] The other explanation, no longer believed to be accurate,[7] is fusion, in which the fertilized egg completely separates, but stem cells (that search for similar cells) find similar stem cells on the other twin and fuse the twins together. Conjoined twins share a single common chorion, placenta, and amniotic sac in utero, but so do some monozygotic but non-conjoined twins.[8]
Chang and Eng Bunker (1811–1874) were brothers born in Siam (now Thailand) who traveled widely for many years and were known internationally as the Siamese Twins. Chang and Eng were joined at the torso by a band of flesh and cartilage, and by their fused livers. In modern times, they could easily have been separated.[9] Due to the brothers' fame and the rarity of the condition, the term Siamese twins came to be associated with conjoined twins.
- ^ "conjoined twin". Encyclopedia Britannica. Retrieved November 5, 2021.
- ^ "Medical Definition of Conjoined twin". MedicineNet. Retrieved November 5, 2021.
- ^ Maymon, Ron; Mendelovic, Sonia; Schachter, Morey; Ron-El, Raphael; Weinraub, Zwi; Herman, Arie (September 2005). "Diagnosis of conjoined twins before 16 weeks' gestation: The 4-year experience of one medical center". Prenatal Diagnosis. 25 (9): 839–843. doi:10.1002/pd.1274. PMID 16170850. S2CID 32204640.
- ^ Schiewe, Mitchel C.; Whitney, John B.; Anderson, Robert E. (February 1, 2015). "Potential risk of monochorionic dizygotic twin blastocyst formation associated with early laser zona dissection of group cultured embryos". Fertility and Sterility. 103 (2): 417–421. doi:10.1016/j.fertnstert.2014.11.009. PMID 25516079.
one could predict dizygotic conjoined twins occurring less than 1 in every 4.7 billion ovulation cycles
- ^ a b Carnevale, Francisco Cesar; Borges, Marcus Vinicius; Affonso, Breno Boueri; Pinto, Ricardo Augusto de Paula; Tannuri, Uenis; Maksoud, João Gilberto (April 2006). "Importance of angiographic study in preoperative planning of conjoined twins: case report". Clinics. 61 (2): 167–70. doi:10.1590/S1807-59322006000200013. PMID 16680335.
- ^ Conjoined Twins at eMedicine
- ^ a b Kaufman, M.H. (August 2004). "The embryology of conjoined twins". Child's Nervous System. 20 (8–9): 508–25. doi:10.1007/s00381-004-0985-4. PMID 15278382. S2CID 206964928.
- ^ Tao Le; Bhushan, Vikas; Vasan, Neil (2010). First Aid for the USMLE Step 1: 2010 20th Anniversary Edition. USA: The McGraw-Hill Companies, Inc. p. 121. ISBN 978-0-07-163340-6.
- ^ "h2g2 – Twins – A369434". Bbc.co.uk. Retrieved August 3, 2014.
Cite error: There are <ref group=lower-alpha> tags or {{efn}} templates on this page, but the references will not show without a {{reflist|group=lower-alpha}} template or {{notelist}} template (see the help page).