The Twins Who Have Different Fathers

A woman in New Jersey discovered that her twins were fathered by two different men during a paternity case. During her testimony, she admitted to sleeping with a man who was different from her partner a week after she thought she conceived the twins, the New York Times reports.

The mother of twins was applying for public assistance in Passaic County, N.J. However, the case took a shocking turn when it was discovered that the man who the woman said was the father of her twins was deemed responsible for only one.

The man originally described as the twins’ father will only have to pay child support for the toddler whose DNA test showed was reliably his own child.

But how is it possible? 

Jennifer Wu, an obstetrician-gynecologist at Lenox Hill Hospital in Manhattan, called it a case of superfecundation, a rare phenomenon.

Superfecundation is the fertilization of two or more ova from the same cycle by sperm from separate acts of sexual intercourse, which can lead to twin babies from two separate biological fathers. The term superfecundation is derived from fecund, meaning the ability to produce offspring.

A sperm can be viable for up to five days, Dr. Wu said. So if the mother in this case had sex with one of the men, ovulated, and then had sex with the other — all within the course of just under a week — one man’s sperm could have fertilized one egg, while the other’s fertilized another.

Michael Carroll, a reproductive scientist at Manchester Metropolitan University, explains that although rare in humans, superfecundation is common in dogs, cats and cows. “Females will have multiple matings with multiple males and this increases the chance of them producing multiple offspring.” Humans, on the other hand, “are not the best at breeding”. 

Either way, “It’s extremely uncommon,” Carroll says. “It all adds up to many rarities happening in the same cycle.” A sperm’s journey is arduous at the best of times. To have two successful candidates from two different men in a month when two eggs happen to be released … Well, what are the odds?