According to doctors, if a woman has more than one sexual partner while she is ovulating, there is a chance that different sperm cells can fertilize two separate eggs.
It's called "heteropaternal superfecundation." Experts say it's more common in animals. The first recorded human case was in 1810.
Scientists say superfecundation most commonly happens within hours or days of the first instance of fertilization. Sperm cells can live inside a woman's body for 4 to 5 days. And once ovulation occurs, the egg remains viable for 12 to 48 hours before it begins to disintegrate. So the fertile period can last from 5 to 7 days.
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