MAR 11, 2016 06:06 AM PST

A Rare Case of Twins with Different Fathers

WRITTEN BY: Xuan Pham

A couple in Vietnam recently received some shocking news about their two-year-old twins: they have different fathers. A local report stated that the twins are of the same gender, but "one has thick and wavy hair, while the other has thin and straight hair." Urged by family members who thought there might have been a mix-up at the hospital, the family underwent genetic testing at the Vietnam Genetic Association clinic in Hanoi. The tests revealed that the twins share the same DNA as the mother, but not the same father.

In a statement to the press, Professor Le Dinh Luong, president Vietnam Genetic Association, said the results were 100% correct in what he called "an extremely rare case." Indeed, the case of bi-paternal twins is a first for Vietnam, and is part of less than 10 known cases in the world.

The condition is formally known as heteropaternal superfecundation, meaning sperm from more than one male fertilized eggs in a very fertile female. The odds are rare, but overlap in fertilization can happen if a woman has intercourse with different partners within a short time. According to Dr. Keith Eddleman, Director of Obstetrics at Mount Sinai Hospital, "A woman's egg has a life span of 12 to 48 hours, and a sperm is viable for seven to 10 days, so there's about a week's time for potential overlap and the fertilization of two eggs by two sperm from separate acts of sexual intercourse."

Rare, interesting, and awkward. Watch to learn more!
About the Author
  • I am a human geneticist, passionate about telling stories to make science more engaging and approachable. Find more of my writing at the Hopkins BioMedical Odyssey blog and at TheGeneTwist.com.
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