When they were born, Abigail and Brittany Hensel's parents were told they would likely not survive more than a few hours. Their case is rare. Twins have two hearts, two lungs, two stomachs and two separate brains. However, they are born with dicephalic parapagus. This means they were born with two heads but only one body. From the waist down they share all the organs. Brittany controls the left side of the body, while Abigail controls the right. The University of Maryland Medical Center reports that “Conjoined twins occur once in every 200,000 births.” To understand the life of conjoined twins, it is necessary to first understand how this phenomenon occurs, the separation procedures and the ethical issues that arise. plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an Original Essay First, it is important to understand how conjoined twins are born. According to the Encyclopedia of Diseases and Disorders, conjoined twins are identical twins in which the two embryos have not completely separated before the baby is born. The disorder results from the failure of embryos to divide after the twelfth day of fetal development. When a fertilized human egg manages to divide before the twelfth day, twins will be born separately. The longer it takes the embryos to divide, the more complicated the interconnection of the baby's body will be. The University of Maryland Medical Center states that “about 40 to 60 percent of conjoined twins are stillborn, and about 35 percent survive only a day. The overall survival rate of conjoined twins is between 5% and 25%.” Female sisters appear to be more likely to survive than their male siblings, females are three times more likely than males to be born alive. About 70% of all conjoined twins are girls. Secondly, in most cases, the separation surgery will take place once the twins are 4 months old. Waiting gives the child's body a chance to grow. This makes it easier for doctors to perform the surgery and makes the surgery easier on the child's body. According to the American Pediatric Surgical Association. only about 250 separation surgeries have been successful, meaning that at least one twin survived for a long period of time. There are different categories of conjoined twins, which means that each separation procedure is different. According to Medscape, which is a leading medical resource for doctors, medical students, nurses and other healthcare professionals, 74 percent of conjoined twins are connected at the thorax, abdomen, or both. To divide twins joined at the torso, the surgeon first breaks the skin, then must carefully divide the organs and donate enough of the organ to both bodies, making sure to avoid major arteries and veins. The severed organs are then stitched back together and placed back into individual bodies before the skin itself is stitched together. Ultimately, whether or not twins can be successfully separated depends on how many organs or how many organs they share. Many ethical complications can arise from separation or the decision not to separate. The decision to separate conjoined twins would be easy if the survival of both individuals was guaranteed, however this is not always possible. In some cases, separation would pose serious health risks to one or both twins. An example of this occurred in head-connected two-year-old twins. The girls, who were unnamed, shared their kidneys and the veins that regulate blood in their brains. The separation surgery was very unlikely to benefit.