Savior siblings are a relatively new concept in the medical world. Put simply, savior siblings are children conceived in order to save a terminally ill older sibling by donating gene-compatible body tissue or organs. The first known savior sibling was born in 2000, leaving less than 20 years for the ethical arguments in favor of and against savior siblings to take shape.
While savior siblings provide a unique opportunity to save the life of an already living child, many ethicists believe the production of children who exist to serve their older siblings violates important moral codes. On the other hand, the success of savior siblings as a viable medical option is undisputable. As science advances far beyond what humans once thought possible, moral codes struggle to keep up with the technology of the times. The history of savior siblings may be short, but their real and perceived impact on the world has vast implications for the future of reproductive science.
In 2000, Adam Nash became the first known savior sibling. Born in the United States, Adam was conceived to save his older sister, Molly, who was diagnosed with Fanconi anemia shortly after birth. Molly's specific type of anemia is extremely rare. In addition to an increased risk of developing certain cancers, Molly also had a 90% chance of developing bone marrow failure. In order to save her life, doctors recommended the conception of a savior sibling who might share the same Human Leukocyte Antigen (HLA) genes as Molly.
Through preimplantation genetic diagnosis (PGD) and in vitro fertilization (IVF), Adam Nash was conceived. After his birth, Adam donated his umbilical cord to his sister. His tissue saved Molly's life, and thus the concept of savior siblings became a viable medical option to quickly save terminally ill children.
When it comes to creating savior siblings, the process usually follows the same rough pattern as Adam Nash's conception. Since children born from the same parents only have a one-in-four chance of sharing compatible HLA genes, Adam's parents decided to increase their odds by creating a designer baby.
Before Adam's embryo was implanted into his mother, various sperm and eggs were collected in a petri dish and tested for compatible HLA genes. Once doctors matched HLA genes of the embryo to those of Molly, that specific embryo was used in the fertilization process. Using this method, Adam's parents guaranteed their new child would match his older sister, ensuring that they could save the life of their daughter instead of gambling on a second child whose HLA genes might not match.
PGD and IVF were both developed for other purposes. In the context of savior siblings, however, these techniques allow doctors to screen embryos prior to conception to determine compatibility with the tissue of the sick child. It is believed that around 1% of PGD in the United States is used to create savior siblings whose HLA genes are a match for their siblings.
Donor children often save the life of their older sibling by donating stem cells that can be gleaned from umbilical cord blood or bone marrow. While outside donors are certainly a possibility, finding a perfect match is nearly impossible. In the case of Fanconi anemia sufferers, such as Molly Nash, the best chance of survival comes from a transplant from a perfectly matched sibling donor.
Before 1982, successful treatment for Fanconi anemia children did not exist. When doctors discovered the existence of HLA genes and their impact on donor recipients, they were able to carry out transplants on Fanconi patients without causing fatal cell damage.
Eventually, scientists discovered that umbilical cord blood from a sibling donor could be used as an even more successful transplant option. In 1995, the odds of survival from a sibling cord blood transplant were 85%, while the odds of survival from a nonrelated donor were just 30%. In the case of ailing children like Molly Nash, a savior sibling may be their only chance at survival.
The primary reason to use PGD and IVF is to make certain the new child has compatible tissue with its older sibling; they also, however, ensure the new baby won't inherit the same illness. Parents could try for a second child using natural processes, but many of the afflictions of the terminally ill older sibling could just as easily appear in a naturally conceived new child.
In the case of the Nash family, PGD and IVF were a life-saving choice for both Adam and Molly. Fanconi anemia is an inherited condition. When it appeared in Molly after birth, both parents confirmed they were carriers of the genes for the disease. Any future children who were naturally conceived ran the risk of suffering the same disease as Molly. By using PGD and IVF, the Nashs confirmed their new embryo matched Molly's tissue and simultaneously verified that their new child did not carry the Fanconi anemia gene.