Twin babies with different fathers: How does it happen?

Bollywood comedy drama ‘Bad Newz’ starring Vicky Kaushal and Triptii Dimri in the lead roles deals with a unique medical condition. In the film, the heroine gives birth to twin babies with different fathers. One might think the condition is fictional, and it is even featured in the famous 1988 Lindsay Lohan-starred Hollywood film, The Parental Trap. However, it's no made-up condition. This rare condition is called heteropaternal superfecundation.

What causes the condition?
Heteropaternal superfecundation occurs when two or more eggs from the same menstrual cycle are fertilized by sperm from different men. Even though a rare phenomenon, heteropaternal superfecundation is scientifically possible. This type of pregnancy, which is commonly seen in animals like dogs, cats and cows, has been reported in humans too, though rarely.

Superfecundation happens when a woman releases more than one egg or ova in the same menstrual cycle. She should also have sexual intercourse with different men within a short time frame during ovulation. Sperms can stay alive in the reproductive system of a woman for up to five days. During this time, sperm from different men fertilize different ova to produce zygotes. Such fertilization could lead to the birth of twins or more babies. The paternity of the babies born like this could be established through DNA tests.

Cases of heteropaternal superfecundation have been reported in countries like the US, Brazil and Columbia. Around twenty cases of such rare births have been reported across the globe. News of heteropaternal superfecundation that was reported in 2022 was the inspiration for the Bollywood movie ‘Bad Newz’. Meanwhile, the birth of the twin half–brothers Castor and Pollux in Greek and Roman mythology is said to have happened due to heteropaternal superfecundation.