Superfecundation

Superfecundation or heteropaternal superfecundation, is an extremely rare phenomenon. It occurs when a second egg is released during the same menstrual cycle. This second oocyte is fertilized by another man's sperm during the next intercourse that takes place within a short time after the first oocyte is fertilized.

This phenomenon was first described by Archer in 1810, who presented dizygotic twins that differed phenotypically. They were two women, one of whom was mulatto and the other white. It is mentioned that, thanks to the current possibilities of molecular biology and the growing popularity of paternity tests, it may become an increasingly common phenomenon.