In the New York Times this week, coverage on an unusual case. NYT reporter Heather Murphy wrote about the story of a man whom researchers are studying because he had received a stem cell transplant, and subsequent DNA testing revealed unusual results.

Umbilical cord blood donation allows a type of stem cell transplant.

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?

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.