A woman gave birth to two babies who have different fathers after having sex with two men in one day. The 19-year-old had a DNA test done on the twins when they were eight months old in a bid to determine who the father was.
But the test to match a man she thought was father to both of her twins came back positive for just one of the babies.
The woman, who has asked not to be named, said: "I remembered that I had had sex with another man and called him to take the test, which was positive. "I was surprised by the results. I didn't know this could happen and the babies are very similar."
The birth certificate still registers just one man as the father of both children, with the mother, reports the Star. She added: "He takes care of both of them, helps me a lot and gives them all the necessary support that they need."
Dr Tulio Jorge Franco has been studying the unusual pregnancy, which is understood to be only the 20th known case of heteroparental superfecundation.
The doctor explained to Portuguese news outlet G1 that such a pregnancy happens when "two eggs from the same mother are fertilised by different men. The babies share the mother's genetic material, but they grow in different placentas".
He added: "The pregnancy was super smooth, without any complications. The boys were born healthy and have never had health problems.
"It's extremely rare. It happens once in a million. I never imagined that I would see such a case in my life."
The doctor made the decision to disclose the story this week with the twin babies now one year and four months old. The mother is from the small Portuguese town of Mineiros in the state of Goias.
