Superfecundation is the fertilization of two or more ova from the same cycle by

sperm Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as a flagellum, ...

from separate acts of

sexual intercourse Sexual intercourse (or coitus or copulation) is a sexual activity typically involving the insertion and thrusting of the penis into the vagina for sexual pleasure or reproduction.Sexual intercourse most commonly means penile–vaginal pene ...

, which can lead to twin babies from two separate biological fathers. The term superfecundation is derived from fecund, meaning the ability to produce offspring. Homopaternal superfecundation is fertilization of two separate ova from the same father, leading to

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

, while heteropaternal superfecundation is a form of atypical twinning where, genetically, the twins are half siblings – sharing the same mother, but with different fathers.

Conception

Sperm cells can live inside a 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 is normally suspended during

pregnancy Pregnancy is the time during which one or more offspring develops ( gestates) inside a woman's uterus (womb). A multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occurs by sexual intercourse, but ...

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 Superfetation (also spelled superfoetation – see fetus) is the simultaneous occurrence of more than one stage of developing offspring in the same animal. In mammals, it manifests as the formation of an embryo from a different menstrual cycle w ...

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.

Cases in Greek mythology

Greek mythology A major branch of classical mythology, Greek mythology is the body of myths originally told by the ancient Greeks, and a genre of Ancient Greek folklore. These stories concern the origin and nature of the world, the lives and activities o ...

holds many cases of superfecundation: * Leda lies with both her husband Tyndareus and with the god

Zeus Zeus or , , ; grc, Δῐός, ''Diós'', label= genitive Boeotian Aeolic and Laconian grc-dor, Δεύς, Deús ; grc, Δέος, ''Déos'', label= genitive el, Δίας, ''Días'' () is the sky and thunder god in ancient Greek relig ...

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

Helen Helen may refer to: People * Helen of Troy, in Greek mythology, the most beautiful woman in the world * Helen (actress) (born 1938), Indian actress * Helen (given name), a given name (including a list of people with the name) Places * 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 (; Ancient Greek: Ἀλκμήνη or Doric Greek: Ἀλκμάνα, Latin: Alcumena means "strong in wrath") was the wife of Amphitryon by whom she bore two children, Iphicles and Laonome. She is best ...

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 ; grc, Ἰφικλῆς ''Iphikles''), also called Iphiclus, was the maternal half-brother of Heracles and one of the Calydonian boar hunters. Family Iphicles was the son of Alcmene and her human husband ...

by Amphitryon and

Heracles Heracles ( ; grc-gre, Ἡρακλῆς, , glory/fame of Hera), born Alcaeus (, ''Alkaios'') or Alcides (, ''Alkeidēs''), was a divine hero in Greek mythology, the son of Zeus and Alcmene, and the foster son of Amphitryon.By his adoptiv ...

by Zeus. * Chione lies with both

Apollo Apollo, grc, Ἀπόλλωνος, Apóllōnos, label=genitive , ; , grc-dor, Ἀπέλλων, Apéllōn, ; grc, Ἀπείλων, Apeílōn, label=Arcadocypriot Greek, ; grc-aeo, Ἄπλουν, Áploun, la, Apollō, la, Apollinis, label= ...

and

Hermes Hermes (; grc-gre, Ἑρμῆς) is an Olympian deity in ancient Greek religion and mythology. Hermes is considered the herald of the gods. He is also considered the protector of human heralds, travellers, thieves, merchants, and orat ...

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

Autolycus In Greek mythology, Autolycus (; Ancient Greek: Αὐτόλυκος ''Autolykos'' 'the wolf itself') was a successful robber who had even the power of metamorphosing both the stolen goods and himself. He had his residence on Mount Parnassus and ...

for Hermes and Philammon for Apollo.

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 supported that the twinning was not a result of the embryos splitting, and that all five boys shared the same father. In 2015, a judge in

New Jersey New Jersey is a state in the Mid-Atlantic and Northeastern regions of the United States. It is bordered on the north and east by the state of New York; on the east, southeast, and south by the Atlantic Ocean; on the west by the Delawa ...

ruled that a man should only pay child support for one of two twins, as the mother had sex with two different men within a week. In 2016, 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 a twin from two different fathers with whom she had sex on the same day.

Conception

Heteropaternal superfecundation

Cases in Greek mythology

Selected cases involving superfecundation

See also

References

Further reading