A “savior sibling,” also known as a donor sibling, is a child conceived through assisted reproductive technology (ART) specifically to provide biological material to treat a pre-existing sibling with a severe, life-threatening condition. The goal is to find a newborn who is a perfect tissue match for the sick child, typically to donate hematopoietic stem cells. These stem cells are found within the umbilical cord blood and are collected at birth without physical risk to the donor child. This intervention is sought by parents facing a dire prognosis for their older child due to diseases like Fanconi anemia, beta-thalassemia, or certain leukemias.
The Medical Technology Enabling Savior Siblings
The conception of a savior sibling requires a highly specialized combination of in vitro fertilization (IVF) and genetic screening. The process begins with standard IVF, where eggs are retrieved and fertilized in a laboratory setting to create multiple embryos. This pool of embryos is necessary for subsequent genetic analysis and selection.
The next step is Preimplantation Genetic Diagnosis (PGD), performed on cells biopsied from each developing embryo. PGD screens for two genetic characteristics. First, it ensures the embryo is free of the specific genetic disorder affecting the older sibling, preventing the birth of another affected child.
Simultaneously, the PGD process includes Human Leukocyte Antigen (HLA) typing, which is a tissue-matching test. HLA markers are proteins on the surface of most cells, and a close match is necessary for a successful stem cell transplant, minimizing the risk of rejection. Since a naturally conceived sibling has only a one-in-four chance of being a perfect HLA match, PGD allows for the selection and transfer of only the embryos that meet both the disease-free and HLA-matched criteria.
Global Data on Births and Prevalence
Obtaining precise, annual global statistics on the number of savior siblings born is challenging because there is no mandatory, centralized international reporting system for this specific application of PGD. Data is generally collected by individual clinics, national regulatory bodies, or through collaborative studies, making a definitive count impossible. The procedure remains a rare intervention compared to the overall number of children born via IVF.
The best available data comes from collaborative registries, such as a multi-center study published in 2018 by the European Society of Human Reproduction and Embryology (ESHRE). This study tracked procedures over 15 years across 14 centers and reported a cumulative total of only 136 HLA-matched babies born. This figure suggests that the annual number of births resulting from this specific procedure remains in the low double digits across reporting centers worldwide.
The low prevalence is also due to the low success rate of the entire process, as couples must overcome several biological hurdles. For a couple with a child affected by a single-gene disorder, the chance of any given embryo being both disease-free and a perfect HLA match is significantly less than 25 percent. An estimated one percent of all PGD procedures in the United States are performed for tissue matching, illustrating the narrow scope of this medical application. The procedure is reserved for severe hematopoietic disorders like beta-thalassemia, where an HLA-matched sibling donor offers the highest chance of a successful stem cell transplant.
The Laws Governing Savior Sibling Creation
The creation of a savior sibling is an ethically debated application of assisted reproductive technology, leading to significant variations in legal frameworks across the globe. This patchwork of regulations limits the overall number of procedures performed worldwide. Many jurisdictions attempt to balance the desire to save a child’s life with the ethical concerns surrounding conception for the purpose of donation.
In the United States, there is no federal law specifically governing the use of PGD for HLA matching, generally permitting the procedure under the discretion of medical professionals and ethics boards. This contrasts sharply with many other countries that have established strict regulatory frameworks. For instance, the United Kingdom, through its Human Fertilisation and Embryology Authority, allows the procedure but requires pre-approval and oversight.
A key legal distinction is the “dual-purpose” rule. This rule, adopted in countries like Australia, mandates that PGD for HLA matching is permissible only if the embryo is also screened to ensure it is unaffected by the genetic disease in the family. This approach prevents the creation of a savior sibling solely for the purpose of donation when no genetic disease is present. Other countries, particularly in Europe, have either tightly restricted or banned the procedure, viewing the conception of a child primarily as a means to an end for another person.