Out of approximately every 400, 000 births, four are conjoined. Of the four, three will die within twenty-four hours. Of the remaining set of twins, 70% of them will either die (one or both) or they will live out their lives handicapped. The overall survival rate for conjoined twins is between 5% and 25%. Considerably more males conjoin in the womb than females; however females are three times as likely as males to be born alive. Approximately 70-75% of conjoined twins are female.

Conjoined twins who survive are truly miracle babies. They are a medical phenomenon, and even more so in society, for the survival rate of conjoined twins is so low that meeting conjoined twins that survived is a rare occasion. Conjoined twins, defined by Stedman's Medical Dictionary, is:" Identical twins born with their bodies at some point and having varying degrees of residual duplication, a result of the incomplete division of the ovum from which twins developed." Simply put, conjoined twins are twins whose bodies are joined together at birth. There are many different names for conjoined twins, however the two most common are conjoined and Siamese. The word Siamese most likely originated from the twins Chang and Eng who were from modern day Thailand. Both words however refer to twins who are a form of monozygotic twins.

Monozygotic twins are formed when a single fertilized egg splits into two embryos. Or perhaps in an easier to understand way, conjoined twins are formed when the zygote (a cell that is the result of fertilization) of identical twins fails to completely separate. This failure of the zygote to completely separate is not affected by heredity, infertility treatments, maternal age, or any other factors. The cause of the birth of conjoined twins is really unknown, and at this point completely random.

There are several conjoined twins now present in the world, most of which have been featured in some kind of news article or TV show. Some of the most famous conjoined twins are Chang and Eng Bunker, and Mary and Eliza Chulkhurst. Chang and Eng were Chinese Americans born modern day Thailand in 1811 and are most likely responsible for the term Siamese Twins being coined. Mary and Eliza are the earliest known set of conjoined twins. They were born in 1100 in Bidden den, Kent, England. There are many different types of conjoined twins, depending upon where the twins are joined together.

These types include: Thoracopagus (bodies fused in the thorax), Omphalopagus (joined at the lower chest), Xiphopagous (bodies fused in the xiphoid cartilage), Pygopagus (joined back to back to the buttocks), Cephalopagus (heads fused, bodies separated), Cephalothoracopagus (bodies fused in the head and thorax), Craniopagus (skulls fused), Craniopagus parasitic us (a second body less head attached to the head), Dicphalus (two heads, one body with two legs and two arms), Ischopagus (anterior union of the lower half of the body, not involving the heart), Parapagus (lateral union of the lower half of the body), and Diprosopus (one head, with two faces side by side). The most common type of conjoined twins is Thoracopagus. In some cases, parts of the brain have been known to be shared between the conjoined twins in the cranial cavity. Conjoined twins, from the moment they enter the world, face a myriad of social, physical, psychological, and health problems. Occasionally one of the twins will fail to develop properly, effectively acting as a parasite upon the normally developed twin; this condition is known as parasitic twinning or asymmetric conjoined twins. If one or both of the conjoined twins' major body parts cannot properly function, they usually die within a few days.

Separation of the twins is very rarely an option that will prove successful; depending however a lot upon where the twins are conjoined. Each conjoined twin is different, and each one has equally difficult health problems. Some conjoined twins share a heart, or the circulatory system, or are Thoracopagus and only have two arms or even Parapagus and have only two legs. Separation of conjoined twins has been successful; however the operation is a dangerous one. In the past century, technology has advanced rapidly.

So rapidly in fact, that separating twins in the past fifty years has been extremely successful. There have been two hundred attempted surgical separations of conjoined twins, and since 1950 three-fourths of those attempted separations have resulted in one or both of the twins surviving. Wallace, Irving, and Amy Wallace. The Two. New York, New York. : Simon and Schuster, 1978." Stuck on You." DVD-ROM.

20 th Century Fox. 2003 Conjoined Twins. BBC. 2000 web twins. shtml Frequently Asked Questions About Conjoined Twins. Pamela Ferro.

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