Conjoined Twins

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 Biddenden, 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 parasiticus (a second bodyless 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,