A Washington man and his partner were stunned to discover that the father of their IVF baby was not the man himself, but his unborn twin brother. This astonishing case, reported in 2015, highlights a rare medical phenomenon known as vanishing twin syndrome.
The Shocking Discovery
After undergoing fertility treatments and having a son, the couple was shocked when two paternity tests revealed that the 'dad' only shared 10% of his child's DNA. Fearing a mix-up at the IVF clinic, they hired a lawyer who contacted Barry Starr's Ask a Geneticist blog, bringing the case to light.
Dr Starr, then director of outreach at Stanford University's Department of Genetics, suggested a full genetic analysis with 23andMe to trace their ancestry. The results revealed that the boy's 'father' was actually his uncle - his father's twin brother, who was never born.
Vanishing Twin Syndrome Explained
Vanishing twin syndrome occurs when one twin dies early in utero and is absorbed by the other fetus. It happens in as many as 20 to 30% of twin pregnancies, but often the twin is absorbed by the mother's placenta. In this case, the man absorbed his twin's cells directly, becoming a 'chimera' of himself and his brother.
"That was kind of a eureka moment," Dr Starr told Buzzfeed, explaining that they realized the man must be a chimera. He added: "Chimera reports are very rare, but they are real."
Scientific Significance
Dr Starr's team reported their findings in 2015 at the International Symposium on Human Identification in Grapevine, Texas, and the American Society for Human Genetics Annual Meeting in Baltimore, Maryland. This case remains one of the strangest in medical history, demonstrating the complexities of human genetics and reproduction.
