A Brazilian mom had a one-in-a-million conception as she delivered twins, but they have different biological fathers.
The 19-year-old gave birth to twins nine months after she had sex with two men on the same day. Local news outlet Globo reported that she began having doubts over who their dad was as the twins' first birthdays loomed, so she decided to take a paternity test to confirm her suspicions.
The anonymous mom initially suspected only one of the two men to be the dad of the twins, so she collected his DNA. The sample only turned up positive for one child.
What is heteropaternal superfecundation?
The woman, who asked not to be identified, said she remembered that she had sex with another man and called him to take the test, which was positive. She told the outlet that she was surprised by the results and did not know this could happen.
While this phenomenon is jaw-dropping, it is certainly not impossible. Dr. Tulio Jorge Franco, the woman's attending physician, said in an interview that it is possible to happen when different men fertilize two eggs from the same mother. He explained that the babies share the mother's genetic material but grow in separate placentas.
According to Biomedica, heteropaternal superfecundation is an extremely rare phenomenon that happens when a second ova released during the same menstrual cycle is additionally fertilized by the sperm cells of a different man in separate sexual intercourse.
Dr. Franco admitted he never thought he would see a situation such as this in his lifetime as the odds of this happening is one in a million. He claims there are only about 20 other instances in the world like it.
Twins being looked after by just one of the fathers
The mom said that the twins, who are now 16 months old, are currently looked after by just one of the dads. It is unclear at the moment if the other father plays any role in their lives.
These unique twins are not the first to grab international headlines, according to the New York Post. A judge ruled in 2015 that a New Jersey dad only had to pay child support for one of two twins because he only fathered one.
DNA expert Karl-Hans Wurzinger's testimony during the controversial case cited an academic study he published in 1997 that found that different dads occur in about one out of every 13,000 reported paternity cases involving twins.
Dr. Keith Eddleman, who was the director of obstetrics at New York's Mount Sinai Hospital, told CNN at the time of the trial that since an egg is viable for 12 to 48 hours and a sperm has a life span of seven to 10 days, there is about a week's time for potential overlap. He added that the fertilization of two eggs by two sperm from two separate acts of intercourse with different men is indeed possible.
