Umbilical cord blood donation allows a type of stem cell transplant. This is my third post specifically about stem cell transplants and ancestry testing and it’s the first that focuses specifically on umbilical cord blood. You can read the first two about a case of bone marrow transplantation affecting an ancestry test result and how to try to go about DNA testing if you have already received a stem cell donation:
The New England Journal of Medicine recently released a paper on an extremely rare set of boy/girl sesquizygotic twins. Early in the pregnancy, it was noted on ultrasound that the twins shared a placenta, indicating they were likely identical twins. Sesquizygotic twins have been reported in the literature before, but this is reportedly the first case of it being detected during a pregnancy.
What happens to DNA when someone has a stem cell transplant?
Some people have had a stem cell transplant using their own stem cells. This type of transplant does not have any impact on DNA and DNA test results. Organ transplants also do not appear to impact DNA results, even though the organ has come from a different person whose DNA differs from you.
Those who have had stem cell transplants in which they’ve received a stem cell donation from another person run into challenges when having a DNA test on blood or saliva. After transplant, the white blood cells circulating through the body contain the DNA of the stem cell donor because the blood-producing cells of the bone marrow have been replaced by the donor’s. Red blood cells are essentially sacks of hemoglobin and don’t contain DNA, so only white blood cells are the issue.
When you have an allogeneic bone marrow or stem cell transplant, the blood-producing cells in your bone marrow are killed off by radiation or chemotherapy and then replaced with functioning cells from another person. The technical term for this process is allogeneic hematopoietic cell transplantation.