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Superfecundation is the fertilisation of two or more ova from the same cycle by sperm from separate acts of sexual intercourse. The term is also sometimes used to refer to the instances of two different males fathering fraternal twins, though this is more accurately known as heteropaternal superfecundation. This therefore leads to the possibility of twins also being half-siblings.
Conception
Superfecundation most commonly happens within hours or days of the first instance of fertilisation with ova released during the same cycle. Ovulation is usually suspended during pregnancy to prevent further ova becoming fertilised and to help increase the chances of a full term pregnancy. However, if an ovum is released after the female was already impregnated when previously ovulating, there is a chance of a second pregnancy -- albeit at a different stage of development. This is known as superfetation.
Heteropaternal superfecundation
Heteropaternal superfecundation is very rare in humans, though more common in other animals. This is primarily due to the predominance of 1:1 heterosexual partner pairings among humans. A woman who has sexual relations with two or more men at short intervals within the same ovulatory period can be impregnated by both men.
There have been noted examples in the past. The classic case, which is discussed in Williams Obstetrics (1980), was recorded in 1810 by John Archer, the first doctor to receive a medical degree in the United States. According to Archer, a white woman who had sex with a black man and a white man within a short time subsequently gave birth to twins--one white, one mulatto. Other cases have been reported since.
One such reported case occured during an episode of the television show Maury. In one particular episode, where a paternity test was taken to find the true father of a guest's twin babies, it was revealed that the twins have different fathers.
Etymology
The term superfecundation is derived from fecund, meaning the ability to produce offspring.
See also
External links
- Heteropaternal Superfecundation
- "Is it possible for fraternal twins to have different fathers?" at The Straight Dope
- An example of heteropaternal superfecundation resulting from group sex can be found in the following journal article:
Lu et al (1994). "Paternity Identification in Twins with Different Fathers". Journal of Forensic Science July; 39(4), 1100-2.
"Superfecundation"