Also found in: Dictionary, Thesaurus, Legal, Encyclopedia, Wikipedia.
monozygotic twins whose bodies are joined. The connection may be slight or extensive; it may involve skin and muscles or cartilage of a limited region, such as the head, chest, hip, or buttock, or the twins may share an organ, such as an intestine or parts of the spine. If joined superficially, the twins may be easily separated by surgery soon after birth. If more deeply united, they may have to go through life with their handicap, if they survive. New techniques in surgery are making it possible to separate some Siamese twins whose physical links are highly complex. Called also conjoined twins
originally, a much-publicized conjoined pair of twins (xiphopagus) born in Siam (present-day Thailand) in the 19th century; this term has since come into general lay usage for any type of conjoined twins, but is incorrect.
Etymology: Chang and Eng, conjoined twins born in Siam (now Thailand) in 1811
conjoined, equally developed twin fetuses produced from the same ovum. The severity of the condition ranges from superficial fusion, such as of the umbilical vessels, to that in which the heads or complete torsos are united and several internal organs are shared. With modern surgical techniques, most Siamese twins can be successfully separated. See also conjoined twins.
Prognosis Depends on the need for or adequacy of surgical separation
'Siamese' twinsConjoined equal twins A joined gestational product due to a failure in division of the yolk sac or due to delayed monovular separation; STs occur in ±1:200,000 term deliveries; most are joined at the chest–thoracopagus Prognosis Depends on adequacy of surgical separation
Si·a·mese twins(sī'ă-mēz' twinz)
A much publicized pair of conjoined twins born in Thailand (then Siam) in the 19th century; this term has since come into general lay usage for any type of conjoined twins.
Siamese twinsIdentical (monozygous) twins that have failed fully to separate after the first division of the ovum and remain partially joined together at birth. The junction is usually along the trunk or between the two heads. From the male twins, Chang and Eng, born in Siam in 1811.
Siamese twins,named for Eng and Chang (1811-1874) who were born in Siam (now Thailand).
identical (monozygotic) twins joined together at birth. The connection may be slight or extensive. It involves skin and usually muscles or cartilage of a limited region, such as the head, chest, hip or buttock. The twins may share a single organ, such as an intestine, or occasionally may have parts of the spine in common. A rare congenital malformation in animals. Called also conjoined twins.