Superfecundation is the fertilization of two or more ova from the same menstrual cycle by sperm from the same or different males, whether through separate acts of intercourse or during a single sexual encounter with multiple males (e.g. double penetration). This can potentially result in twin babies that have different biological fathers. The term superfecundation is derived from fecund, meaning able to produce offspring. Homopaternal superfecundation is a form of twinning where fertilization of two separate ova occurs as a result of two or more distinct instances of intercourse or insemination with the same male partner or donor, leading to

fraternal twins Twins are two offspring produced by the same pregnancy.MedicineNet > Definition of Twin Last Editorial Review: 19 June 2000 Twins can be either ''monozygotic'' ('identical'), meaning that they develop from one zygote, which splits and forms two e ...

. Heteropaternal superfecundation, on the other hand, is an atypical form of twinning that results in twins that are genetically half siblings – sharing the same biological mother, but with different biological fathers.

Conception

Sperm cells can live inside a human female's body for up to five days, and once ovulation occurs, the egg remains viable for 12–48 hours before it begins to disintegrate. Superfecundation most commonly happens within hours or days of the first instance of fertilization with ova released during the same cycle.

Ovulation Ovulation is an important part of the menstrual cycle in female vertebrates where the egg cells are released from the ovaries as part of the ovarian cycle. In female humans ovulation typically occurs near the midpoint in the menstrual cycle and ...

is normally suspended during

pregnancy Pregnancy is the time during which one or more offspring gestation, gestates inside a woman's uterus. A multiple birth, multiple pregnancy involves more than one offspring, such as with twins. Conception (biology), Conception usually occurs ...

to prevent further ova becoming fertilized and to help increase the chances of a full-term pregnancy. However, if an ovum is atypically released after the female was already impregnated when previously ovulating, a chance of a second pregnancy occurs, albeit at a different stage of development. This is known as superfetation.

Heteropaternal superfecundation

Heteropaternal superfecundation is common in animals such as cats and dogs. Stray dogs can produce litters in which every puppy has a different sire. Though rare in humans, cases have been documented. In one study on humans, the frequency was 2.4% among dizygotic twins whose parents had been involved in paternity suits.

Selected cases involving superfecundation

In 1982, twins who were born with two different skin colors were discovered to be conceived as a result of heteropaternal superfecundation. In 1995, a young woman gave birth to diamniotic monochorionic twins, who were originally assumed to be monozygotic twins until a paternity suit led to a DNA test. This led to the discovery that the twins had different fathers. In 2001, a case of spontaneous monopaternal superfecundation was reported after a woman undergoing IVF treatments gave birth to quintuplets after only two embryos were implanted.

Genetic testing Genetic testing, also known as DNA testing, is used to identify changes in DNA sequence or chromosome structure. Genetic testing can also include measuring the results of genetic changes, such as RNA analysis as an output of gene expression, or ...

supported that the twinning was not a result of the embryos splitting, and that all five boys shared the same father. In 2008, on the ''Maury Show'' a paternity test on live television established a heteropaternal superfecundation. In 2015, a judge in

New Jersey New Jersey is a U.S. state, state located in both the Mid-Atlantic States, Mid-Atlantic and Northeastern United States, Northeastern regions of the United States. Located at the geographic hub of the urban area, heavily urbanized Northeas ...

ruled that a man should only pay child support for one of two twins, as he was only the biological father to one of the children. In 2017, an IVF-implanted surrogate mother gave birth to two children: one genetically unrelated child from an implanted embryo, and a biological child from her own egg and her husband's sperm. In 2019, a Chinese woman was reported to have two babies from different fathers, one of whom was her husband and the other was a man having a secret affair with her during the same time. In 2022, a 19-year-old Brazilian from Mineiros gave birth to twins from two different fathers with whom she had sex on the same day.

Mythology

Greek mythology Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of ancient Greek folklore, today absorbed alongside Roman mythology into the broader designation of classical mythology. These stories conc ...

holds many cases of superfecundation: * Leda lies with both her husband

Tyndareus In Greek mythology, Tyndareus (; Ancient Greek: Τυνδάρεος, ''Tundáreos''; Attic Greek, Attic: Τυνδάρεως, ''Tundáreōs''; ) was a Spartan king. Family Tyndareus was the son of Oebalus (or Perieres (king of Messenia), Perieres ...

and with the god

Zeus Zeus (, ) is the chief deity of the List of Greek deities, Greek pantheon. He is a sky father, sky and thunder god in ancient Greek religion and Greek mythology, mythology, who rules as king of the gods on Mount Olympus. Zeus is the child ...

, the latter in the guise of a swan. Nine months later, she bears two daughters:

Clytemnestra Clytemnestra (, ; , ), in Greek mythology, was the wife of Agamemnon, king of Mycenae, and the half-sister of Helen of Sparta. In Aeschylus' ''Oresteia'', she murders Agamemnon – said by Euripides to be her second husband – and the Trojan p ...

by Tyndareus and Helen by Zeus. This happens again; this time Leda bears two sons: Castor by Tyndareus and Pollux by Zeus. *

Alcmene In Greek mythology, Alcmene ( ; ) or Alcmena ( ; ; ; meaning "strong in wrath") was the wife of Amphitryon, by whom she bore two children, Iphicles and Laonome. She is best known as the mother of Heracles, whose father was the god Zeus. Alcmene ...

lies with Zeus, who is disguised as her husband

Amphitryon Amphitryon (; Ancient Greek: Ἀμφιτρύων, ''gen''.: Ἀμφιτρύωνος; usually interpreted as "harassing either side", Latin: Amphitruo), in Greek mythology, was a son of Alcaeus, king of Tiryns in Argolis. His mother was named ...

; Alcmene later lies with the real Amphitryon and gives birth to two sons:

Iphicles In Greek mythology, Iphicles ( or ; ''Iphiklēs''), also called Iphiclus, was the maternal half-twin brother of Heracles and one of the Calydonian boar hunters. Family Iphicles was the son of Alcmene and her human husband Amphitryon, wher ...

by Amphitryon and

Heracles Heracles ( ; ), born Alcaeus (, ''Alkaios'') or Alcides (, ''Alkeidēs''), was a Divinity, divine hero in Greek mythology, the son of ZeusApollodorus1.9.16/ref> and Alcmene, and the foster son of Amphitryon.By his adoptive descent through ...

by Zeus. * Chione lies with both

Apollo Apollo is one of the Twelve Olympians, Olympian deities in Ancient Greek religion, ancient Greek and Ancient Roman religion, Roman religion and Greek mythology, Greek and Roman mythology. Apollo has been recognized as a god of archery, mu ...

and

Hermes Hermes (; ) is an Olympian deity in ancient Greek religion and mythology considered the herald of the gods. He is also widely considered the protector of human heralds, travelers, thieves, merchants, and orators. He is able to move quic ...

on the same night, and falls pregnant. She bears two sons;

Autolycus In Greek mythology, Autolycus (; ) was a robber who had the power to metamorphose or make invisible the things he stole. He had his residence on Mount Parnassus and was renowned among men for his cunning and oaths. Family There are a number of d ...

for Hermes and

Philammon In Greek mythology, Philammon (Ancient Greek: Φιλάμμων) was an excellent musician, a talent he received from his father Apollo. Family Philammon's mother was either Chione (Greek myth), Chione (or Philonis), daughter of Daedalion, or Leuc ...

for Apollo.

Conception

Heteropaternal superfecundation

Selected cases involving superfecundation

Mythology

See also

References

Further reading