Superfetation (also spelt superfoetation - see fetus) is the simultaneous occurrence of more than one stage of developing embryo in the same animal. In mammals it manifests as the formation of a fetus from a different menstrual cycle while another embryo is already present in the uterus. When there are two separate instances of fertilisation during the same cycle, it is known as superfecundation.

Superfetation is claimed to be common in some species of animals, but is extremely rare in humans. In mammals it can occur only where there are two uteri, or where the menstrual cycle continues through pregnancy. The risk with superfetation is that the second baby is often born prematurely, which can increase its odds of experiencing lung development problems.[1]


In animals

Animals that have been claimed to be subject to superfetation include rodents (mice and rats), farm animals (horses and sheep), marsupials (kangaroos and sugar gliders), and primates (humans). Superfetation has also been clearly demonstrated in poeciliid fish [2]

In humans

Reports of superfetation occurring long after the first impregnation have often been treated with suspicion, and some have been clearly discredited. Other explanations have been given (and demonstrated) for different levels of development between twins. Artificially induced superfetation has, however, been demonstrated, although only up to a short period after insemination. In 1960, John and Mary Tress of Baltimore MD had what the nurse called twins, she was wrong. Dr Paul C Weinberg of Mt.Sinai hospital delivered the boys Anthony John and Mark Francis and realized that Anthony born five minutes before his brother Mark looked premature. Immediately Dr Weinberg did x-rays of the boys thigh bones and noticed a disparity in bone age. Mark a full term baby born five minutes after his 2 months premature brother Anthony. Anthony was conceived a full 2 months after his brother Mark, {Newsweek Magazine, July 31. 1961} In 1992, Taylor and Evan Barth, conceived 4 weeks apart, were born in Hawaii, USA to Michelle and John Barth. Taylor, the one conceived later was born first.[citation needed]

In 2007 Ame and Lia Herrity, conceived 3 weeks apart, were born in the United Kingdom to Amelia Spence and George Herrity.[3]

In May 2007 Harriet and Thomas Mullineux, also conceived 3 weeks apart, were born in Benfleet, Essex, UK to Charlotte and Matt Mullineux.[4]

In 2009, Todd and Julia Grovenburg of Fort Smith, Arkansas received international media attention for Mrs. Grovenburg's conception of an additional child while already pregnant with a child conceived two and a half weeks earlier. If it were possible to carry both children to term, the birth of the first child would be expected in December 2009, whereas the second child would be due in January 2010.[5][6] Grovenburg's obstetrician reported that cases of superfetation "can only be confirmed after delivery by chromosomal and metabolic studies on the baby."[7] Both healthy babies were delivered through Caesarean section on 2 December 2010.[8]


  1. ^ Jacob, Stephanie (September 2009). "Superfetation Double Pregnancy". AOL Health. Retrieved September 2009. 
  2. ^ FishBase's glossary.
  3. ^ "Mother Deliveries Babies Minutes Apart but They are Not Twins!", Medindia, 1 October 2007.
  4. ^ Hale, Beth. "The babies born just a minute apart who AREN'T twins", The Daily Mail, Associated Newspapers, Ltd., 15 January 2008.
  5. ^ ABC News: Arkansas Pregnant Woman Is Pregnant Again.
  6. ^ Allen, Nick. "Pregnant woman conceives second child", The Daily Telegraph, 24 September 2009.
  7. ^ Jacob, Stephanie (September 2009). "Superfetation Double Pregnancy". AOL Health. Retrieved September 2009. 
  8. ^ van Sipma, Ashley (2011-07-01). "I got pregnant while I was already pregnant! Woman gives birth to two babies on the same day but they are NOT twins". MailOnline. MailOnline. Archived from the original on 2011-11-01. Retrieved 2011-11-01. 

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Look at other dictionaries:

  • superfétation — [ sypɛrfetasjɔ̃ ] n. f. • 1560; lat. médiév. superfetatio, de superfetare « concevoir de nouveau », rad. fetus → fœtus 1 ♦ Biol. Fécondation de deux ovules, lors de deux ovulations successives (phénomène dont la réalité n a pas été confirmée… …   Encyclopédie Universelle

  • Superfetation — Su per*fe*ta tion, n. [Cf. F. superf[ e]tation.] (Physiol.) The formation of a fetus at the result of an impregnation occurring after another impregnation but before the birth of the offspring produced by it. This is possible only when there is a …   The Collaborative International Dictionary of English

  • superfetation — [so͞o΄pərfē tā′shən] n. [ML superfetatio < L superfetatus, pp. of superfetare < super (see SUPER ) + fetare, to bring forth, impregnate < fetus,FETUS] the fertilization of an ovum during a pregnancy already in existence …   English World dictionary

  • Superfétation —  Ne doit pas être confondu avec Superfécondation. Sur les autres projets Wikimedia : « Superfétation », sur le Wiktionnaire (dictionnaire universel) La superfétation est l implantation d une nouvelle grossesse dans un utérus… …   Wikipédia en Français

  • superfétation — (su pèr fé ta sion) s. f. 1°   Terme de physiologie. Conception d un foetus lorsqu il y en a déjà un dans la matrice. La possibilité de la superfétation chez l homme est très contestée. •   Les juments, quoique pleines, peuvent souffrir l… …   Dictionnaire de la Langue Française d'Émile Littré

  • Superfetation — Su|per|fe|ta|ti|on 〈f. 20〉 Befruchtung von Eiern aus zwei aufeinanderfolgenden Zyklen, was zum Heranreifen von Embryonen unterschiedlichen Alters im Muttertier führt; oV Superfötation [<Super... + lat. foetus „Leibesfrucht“] * * *… …   Universal-Lexikon

  • SUPERFÉTATION — s. f. T. de Physiologie. Conception d un foetus, lorsqu il y en a déjà un dans la matrice.  Il s emploie quelquefois figurément, dans le langage ordinaire, en parlant Des ouvrages d esprit, et il signifie, Rédondance, double emploi de pensée et d …   Dictionnaire de l'Academie Francaise, 7eme edition (1835)

  • SUPERFÉTATION — n. f. Chose qui s’ajoute inutilement à une autre. Ce chapitre est entièrement inutile, c’est une superfétation, une véritable superfétation …   Dictionnaire de l'Academie Francaise, 8eme edition (1935)

  • superfetation — noun Etymology: Medieval Latin superfetation , superfetatio, from Latin superfetare to conceive while already pregnant, from super + fetare to bear young, from fetus newly delivered more at fetus Date: 1642 a progressive accumulation or accretion …   New Collegiate Dictionary

  • superfetation — noun /suːpəfəˈteɪʃən/ a) An excessive accumulation; a superfluous addition. , 1857: These gentlemen were greatly astonished at Bovarys romantic ideas, and the pharmacist hurried in to say to him: This velvet looks to me rather a superfetation.… …   Wiktionary

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