Mid June 2020, Ervina and Prefina, twins conjoined at the top of the head, were separated after an 18 hour surgery, involving over 30 medical professionals, in a Vatican City hospital. This was the first time in history that a set of conjoined twins connected by a shared skull have been successfully, and safely separated. Today the girls are recovering well, and just celebrated their 2nd birthday. But this isn’t the case for all sets of conjoined twins. In many cases, separation means death for one or both of the twins in question. So what do we do when saving one, means killing the other? Conjoined twins were originally called Siamese twins, but that term has been generally phased out of the lexicon. The term referred to conjoined twin brothers Chang and Eng Bunker, born in Siam, now Thailand, in 1811 and touted across the world as circus freaks at the behest of British entrepreneur Robert Hunter in 1829. After their tour, the twins moved to Carolina, married a pair of sisters, and proceeded to have 22 children between them. The causes behind the formation of even regular twins have not been entirely elucidated as of yet. However we do know that women who have children later, that are over the age of 30-40, and women who have had multiple pregnancies prior, have a higher likelihood of producing twins. In addition to that, African women have the highest incidence of twins, while Asian women have the lowest, but the reasons behind this pattern are unknown at this time. The likelihood of conjoined twins occurs about once in every 50-60,000 births, and fascinatingly enough, 70% of conjoined twins are female. One theory posits that females develop quicker than males in utero, which makes them heartier. In fact, Nancy Segal Ph.D. in her paper Twin Types: More Than Just Two, claims that “a newborn female has the physical maturity of a 4–6-week-old male”.If we consider that all mammals begin female in the womb, and maleness only develops after the 2nd month of gestation, then this makes some sense. A female embryo would continue growing on course while a male embryo would have to spend time developing “maleness”, so therefore females would be slightly more developed at birth. Conjoined twins are, as the name suggests, twins that are joined at birth in one way or another. As fraternal twins come from two different fertilized eggs and two entirely separate embryos to start with, they cannot become conjoined. Conjoined twins are essentially just identical twins that haven’t entirely separated before they begin growing in earnest, developing more complicated organs and such without fully becoming two distinct entities. This can lead to any number of health issues both in utero and after birth. Unfortunately the majority of conjoined twins are stillborn, or die shortly after birth. Conjoined twins often share vital organs, leading to unsupportable strain on any number of systems within their shared bodies. A twin that is dependent on the other is usually called an unequal, or asymmetric twin. The health problems that conjoined twins might encounter really depends on the type and nature of their joining. There are 8 different types of conjoined twins, defined by where and how they are joined together. They include: Thoracopagus, often sharing a heart, lungs, or liver between them. These are the most common formations of conjoined twins. Pygopagus, often sharing gastrointestinal tract, and sometimes genitalia and urinary organs. Rachipagus, this formation is very rare, so medical literature is noticeably lacking in information on these kinds of conjoined twins. Omphalopagus, they’ll often share a liver, and sometimes portions of their intestinal tract. Ischiopagus, these twins will usually share gastrointestinal tract, genitalia, urinary organs, and a liver. Sometimes these twins will share 2 sets of legs, or, in some cases, they’ll share 2 or 3 legs between them. Parapagus, they can have anywhere from 2 arms and legs, to 4 of each. Craniopagus, they usually share the same skull, but have separate brains, however they will occasionally share brain matter. Cephalopagus, these twins will share a head, meaning that they will have two faces on a single skull, and share a brain. Unfortunately, these twins rarely survive. So the major concern for medical professionals is how to ensure the health of viable twins after birth. In some cases, separation surgery might be an option, however there are a number of things to consider. We can look to the case of Mary and Jodie, a pair of conjoined twins born on the Maltese island of Gozo in 2000 for insight into the various moral, legal, and ethical ramifications of separation surgery. They were born ischiopagus conjoined twins “linked at the pelvis with fused spines and spinal cords, and four legs”. Jodie was the healthier of the two, and Mary relied on her heart and lungs to survive. If they remained joined, doctors said they wouldn’t last longer than a few months. If an elective separation surgery was performed, then Mary would die, and Jodie would have a 94-95% chance of survival. If they waited for an emergency surgery, then Jodie’s survival rate would decrease to only 40%, and Mary would still definitely die. The parents happened to “decline the option to terminate the pregnancy” when they discovered that their children were conjoined, due to their religious beliefs, and didn’t want to “kill” one child to save the other. Usually the parents’ desire is paramount, but the medical team disagreed with them, so the case went to the Court of Appeal in England, and the judge, Lord Justice Alan Ward, said that “there could not have been the slightest criticism of them for letting nature take its course in accordance with the parents' wishes”, however, “fundamentally the medical team disagreed with it”. In addition to this, the parents noted that “there are few, if any, facilities on their remote island to care for a disabled child”, and there “were virtually no financial resources to provide Jodie's medical treatment at home”. This situation made the decision extremely difficult for the parents, and they were “quite happy for God to decide what happened to their two young daughters”. The judge from Mary and Jodie’s case, Sir Allen Ward, turned to another case from the Children's Hospital of Philadelphia for precedent. In 1977, the deeply religious Jewish parents of a set of conjoined twins were told that they must “sacrifice” one newborn twin to save the other. The parents refused to make a decision without ethical support from their rabbi, the Catholic nurses refused to do the surgery without support from the archdiocese of Philadelphia, and the surgeon, Dr C Everett Koop, refused to go ahead with the surgery “without judicial approval and legal immunity from potential charges of homicide”. Both the Rabbis and Catholic authorities provided analogies to argue why they consented to the surgery for the St Mary Twins. Catholic authorities used an argument by St. Thomas Aquinas that an “evil effect may be permitted if the effect is not intended in itself but is indirect and justified by a commensurate reason”. While the Rabbis suggested something similar: If two men had jumped out of a burning airplane, and only one of their parachutes opened, it would be morally just for the man with the parachute to kick off the man without one if staying together meant they would both die, since he was ostensibly “designated for death” already. Lawyers for the surgeon made similar arguments. They brought up the story of two climbers who, on a trip, lost their footing and found themselves dangling off a cliff face. One climber was secure and holding up the other, but they would both fall if nothing changed. The lawyers argued that it would be perfectly reasonable for the secure climber to cut the rope, even though he knew that it would result in the death of the other climber. Th judges in charge of the Philadelphia case authorized the surgery, but unfortunately, the surviving twin died a few months later. In the end, the judge presiding over the case authorized the surgery for Mary and Jodie. He continued, saying that the remainder of Mary’s life, if left joined, “would not simply be worth nothing to her. They would be hurtful”. So over the course of 20 hours, surgeons worked thoroughly to separate the two, inevitably leading to the death of Mary when doctors cut off her blood supply from Jodie. After the surgery, Jodie recovered at an almost unprecedented rate, being weaned off a ventilator very soon after the operation. Today Jodie lives a healthy life with her parents, and should be entering her early 20s very soon. In an article for the Daily Mail, Sir Allen Ward said that Jodie “is doing extraordinarily well at school and she wants to be a doctor”. Especially when twins share organs like lungs, livers, intestines, or hearts, separating them becomes an almost impossible task. Consider Abigail and Brittany Hensel, a pair of parapagus twins with two torsos fused together and one head each. Separating them would actually limit their autonomy, and even spell death for both of them. Separating conjoined twins is almost always a gamble. Sometimes, like with Mary and Jodie, we get something tragic, yet simple, but sometimes we just can’t save everyone.