The range of occurrence of conjoined twins : 1 in 50,000 births to 1 in 200,000 births, with a higher incidence in India and Africa. The overall survival rate for conjoined twins : Approximately 25%. The condition is more frequently found among females, with a ratio of 3:1.
How do conjoined twins occur? Theory 1 : Fission. A single egg does not fully separate after fertilization. The developing embryo starts to split into identical twins during the first few weeks after conception, but stops before the process is complete. The partially separated egg develops into a conjoined fetus.
Theory 2 : Fusion A fertilized egg separates incompletely. Some cells (which search for similar cells on the other twin ) fuse the twins together. They are called Siamese twins. Siamese twins can't be "conjoined" because they were never separated in the first place. The result is not quite two children. The twins that would have been melt back into a single entity.
The most common types of conjoined twins Thoraco-omphalopagus (28% of cases): Two bodies fused from the upper chest to the lower chest. These twins usually share a heart, and may also share the liver or part of the digestive system.
Thoracopagus ( 胸部連胎 ) (18.5%) : Two bodies fused from the upper thorax to lower belly. The heart is always involved in these cases.
Omphalopagus ( 腹部連胎 ) (10%): Two bodies fused at the lower chest. Unlike thoracopagus, the heart is never involved in these cases; however, the twins often share a liver, digestive system, diaphragm and other organs.
Parapagus ( 寄生式連胎 ) (10%): Twins that are asymmetrically conjoined, resulting in one twin that is small, less formed, and dependent on the larger twin for survival. http://www.youtube.com/watch?v=Z60i1Gl 8Ufc&feature=related Islaam and Manar Maged ----- Cephalopagus parasiticus( 頭部寄生胎 )
Craniopagus ( 頭顱連胎 ) (6%): Fused skulls, but separate bodies. These twins can be conjoined at the back of the head, the front of the head, or the side of the head, but not on the face or the base of the skull.
Other less-common types of conjoined twins include Cephalopagus ( 頭部連胎 ) : Two faces on opposite sides of a single, conjoined head; the upper portion of the body is fused while the bottom portions are separate. These twins generally cannot survive due to severe malformations of the brain.
Diprosopus ( 雙面畸胎 ) Part or all of the face is duplicated on the head. Synecephalus : One head with a single face but four ears, and two bodies http://www.youtube.com/watch?v=Z bC04A9nUmU&feature=related
Cephalothoracopagus ( 頭胸腹聯胎 ) : Bodies fused in the head and thorax. In this type of twins, there are two faces facing in opposite directions, or sometimes a single face and an enlarged skull.
Xiphopagus: Two bodies fused in the xiphoid( 劍胸骨 ) cartilage, which is approximately from the navel to the lower breastbone. These twins almost never share any vital organs, with the exception of the liver. Chang and Eng Bunker
Pygopagus (Iliopagus) ( 臀部連胎 ) : Two bodies joined back-to-back at the buttocks.
Dicephalus: 2 heads, 2 hands and legs, with only one set of organ.
Fetus in fetu: One twin fails to develop past the fetal stage and is completely subsumed into the body of the other. Generally, it's fetus in fetu if the fetus develops a reasonable skeleton, but sometimes there are just bits and pieces of fetus bodies that are subsumed into otherwise healthy babies.
What special treatments do they need in their lives? Some conjoined twins live normally. e.g. Abby & Brittany http://www.youtube.com/watch?v=BkK WApOAG2g&feature=related
But some need device to assist them, for example, Lori and Reba Schappell
Lori and Reba Schappell, As they are different heights, there was a high wheel chair that suited George's unique condition, because to move around. She must be raised to her sister's height, to avoid undue strain upon Lori's neck and back. http://www.youtube.com/watch?v=PvgCaCf_lWc&feature=related
Can conjoined twins be separated? Some surviving conjoined twins can be surgically separated. The success of this surgery depends on 1)where the twins are joined 2)how many organs are shared 3)the experience and skill of the surgical team. Most cases of separation are extremely risky and life-threatening.
The Seo classification of conjoined heart and surgical separability TypeDegree of fusionSeparability INo significant fusionEasy IIFusion of the great vesselsEasy IIIAtrial fusionPossible IIIaMirror image right atrial fusion Possible IIIbOther type of atrial fusionPossible IVAtrioventricular fusionNot possible VSingle heart in one of the twins Not possible
Examples of successful separation of conjoined twins Kendra and Maliyah Herrin http://www.youtube.com/watch?v=5gn HTtcxoPA 2009 >>>>>
BEFORE: Two girls were connected from the breast bone to the navel, and shared a liver and a main blood vessel that connected their hearts. >>>>> 2002 Loice and Christine
Group member: CHENG Tsz Yan 6S (2) TONG Carmen 6S (23)