Case Report of an exceptional spontaneous abdominal heterotopic pregnancy with superfetation: Diagnosis and treatment: Heterotopic pregnancy with superfetation (8+1 WG & 5+4 WG).

Heterotopic pregnancy is an extremely rare condition in which an intrauterine and an extrauterine pregnancy co-exist. In spontaneous conceptions, heterotopic pregnancy occurs in only 1/30 000 pregnancies. The treatment of heterotopic pregnancy must be as minimally invasive as possible to preserve the development of the intrauterine pregnancy. Superfetation, defined as the coexistence of 2 or more foetuses of different gestational ages, remains particularly exceptional and poorly explained (second ovulation? embryonic diapause?). Here, we present an extremely rare case of a spontaneous heterotopic evolutive pregnancy with superfetation, consisting of an embryo in the pouch of Douglas estimated at 8 + 1 weeks of gestation (WG) and a progressive intrauterine pregnancy estimated at 5 + 4 WG. We treated the extrauterine pregnancy with an intra-cardiac injection of potassium chloride echo-guided via the vaginal route, and the patient then underwent exploratory laparoscopy 9 days later and lavage and aspiration of the abdominal heterotopic pregnancy due to pain and biological inflammatory syndrome probably caused by pelvic mass syndrome and peritoneal irritation from the foetal necrosis. She has not yet given birth and is currently at 36 WG.

Tubal superfetation following frozen-thawed single-embryo transfers in two separate cycles: Case report and literature review.

Superfetation is a very rare occurrence. In the context of assisted reproduction, it has been reported only as an intrauterine pregnancy after ovarian stimulation and/or embryo transfer in the presence of an undiagnosed ectopic pregnancy. Here we report a case of a 27-year-old anovulatory patient, gravida 1 para 1, who underwent two frozen-thawed single-blastocyst transfers in separate cycles. The patient reported that 12 days after the first transfer, she had menstrual bleeding and stopped her estradiol and progesterone supplementation without undergoing a blood human chorionic gonadotropin (ßhCG) test. At her request, a second cycle was immediately initiated, with endometrial thickness measuring 4 mm. Eleven days after the second transfer, the ßhCG value was inappropriately high. A right tubal pregnancy corresponding to 8 gestational weeks was diagnosed. Laparoscopy revealed a prominent right tubal pregnancy in addition to a significantly smaller left tubal pregnancy. The discordant tubal pregnancies were confirmed histologically. To our knowledge, superfetation involving a second ectopic pregnancy coexistent with a first, contralateral ectopic pregnancy consequent to consecutive in vitro fertilization procedures has not previously been described in the medical literature. This case emphasizes the importance of routine ßhCG testing after every IVF cycle, even if apparently unsuccessful.

Increased superfetation precedes the evolution of advanced degrees of placentotrophy in viviparous fishes of the family Poeciliidae.

The causes and consequences of the evolution of placentotrophy (post-fertilization nutrition of developing embryos of viviparous organisms by means of a maternal placenta) in non-mammalian vertebrates are still not fully understood. In particular, in the fish family Poeciliidae there is an evolutionary link between placentotrophy and superfetation (ability of females to simultaneously bear embryos at distinct developmental stages), with no conclusive evidence for which of these two traits facilitates the evolution of more advanced degrees of the other. Using a robust phylogenetic comparative method based on Ornstein-Uhlenbeck models of adaptive evolution and data from 36 poeciliid species, we detected a clear causality pattern. The evolution of extensive placentotrophy has been facilitated by the preceding evolution of more simultaneous broods. Therefore, placentas became increasingly complex as an adaptive response to evolutionary increases in the degree of superfetation. This finding represents a substantial contribution to our knowledge of the factors that have shaped placental evolution in poeciliid fishes.

Multiple paternity in superfetatious live-bearing fishes.

Superfetation, the ability to carry several overlapping broods at different developmental stages, has evolved independently multiple times within the live-bearing fish family Poeciliidae. Even though superfetation is widespread among poeciliids, its evolutionary advantages remain unclear. Theory predicts that superfetation should increase polyandry by increasing the probability that temporally overlapping broods are fertilized by different fathers. Here, we test this key prediction in two poeciliid species that each carry two temporally overlapping broods: Poeciliopsis retropinna and P. turrubarensis. We collected 25 females per species from freshwater streams in South-Eastern Costa Rica and assessed multiple paternity by genotyping all their embryos (420 embryos for P. retropinna; 788 embryos for P. turrubarensis) using existing and newly developed microsatellite markers. We observed a high frequency of unique sires in the simultaneous, temporally overlapping broods in P. retropinna (in 56% of the pregnant females) and P. turrubarensis (79%). We found that the mean number of sires within females was higher than the number of sires within the separate broods (2.92 sires within mothers vs. 2.36 within separate broods in P. retropinna; and 3.40 vs 2.56 in P. turrubarensis). We further observed that there were significant differences in the proportion of offspring sired by each male in 42% of pregnant female P. retropinna and 65% of female P. turrubarensis; however, this significance applied to only 9% and 46% of the individual broods in P. retropinna and P. turrubarensis, respectively, suggesting that the unequal reproductive success of sires (i.e. reproductive skew) mostly originated from differences in paternal contribution between, rather than within broods. Together, these findings tentatively suggest that superfetation may promote polyandry and reproductive skew in live-bearing fishes.

A case of heteropaternal superfecundation identified by microhap sequencing of maternal plasma cell-free DNA: A case of HS identified by microhap sequencing.

Heteropaternal superfecundation (HS) refers to the fertilization of two or more oocytes by spermatozoa from different male partners during the polyovulatory period. The present study reported a newly discovered case of HS in the 10th week of gestation, in a case of disputed paternity involving a pair of female twins and two alleged fathers (AF1 and AF2), based on a custom-designed microhap sequencing assay and R package relMix for data interpretation. The results suggested that the twins had different biological fathers, e.g., HS, and indicated the paternity of AF1 in relation to one of the twins while excluding AF2 with regard to both twins. Standard short tandem repeat (STR) analysis was employed to confirm the paternity of the heteropaternal twins. The reported case indicates that HS may occur in paternity cases with dizygotic twins, and microhap, as a novel type of highly polymorphic marker proved to be suitable for mixture deconvolution, should be able to resolve this question effectively and noninvasively at the early stage of pregnancy.

Seven-week asynchronous twins in a buffalo heifer (Bubalus bubalis) associated with superfetation - A case report.

A female buffalo (Bubalus bubalis) of the Bulgarian Murrah breed aged 1,090 days was observed to give birth to a second newborn (normally developed male) after she had calved (normal female) 49 days earlier. This phenomenon is highly associated with her melatonin treatment within a trial for induction of puberty, the last ear implants being placed approximately 50 days before the assumed date of first mating, to which point the level of progesterone had increased dramatically. Despite none of the matings of the dam was visually witnessed to prove ovulation over an existing gestation, we take the liberty to qualify this phenomenon as superfetation, ruling out the other possible phenomena, namely embryonic diapause as it is highly unlikely to occur in any livestock species, and differentiated development of twin foetuses as it is associated with foetal malformation, which was not observed in this case.

Twins from different fathers: A heteropaternal superfecundation case report in Colombia. / Gemelos de diferentes padres: un caso de superfecundación heteropaternal en Colombia

Heteropaternal superfecundation is an extremely rare phenomenon that occurs when a second ova released during the same menstrual cycle is additionally fertilized by the sperm cells of a different man in separate sexual intercourse. In August, 2018, the Grupo de Genética de Poblaciones e Identificación at Universidad Nacional de Colombia received a request to establish the paternity of a pair of male twins with genetic markers. The following analyses were performed: amelogenin gene, autosomal short tandem repeat (STR), and Y-STR analyses by means of human identification commercial kits, paternity index, and the probability of paternity calculation and interpretation. A paternity index of 2.5134E+7 and a probability of paternity of 99.9999% for twin 2 were obtained while 14 out of 17 Y-chromosome markers and 14 out of 21 autosomal short tandem repeats were excluded for twin 1. The results indicated that the twins have different biological fathers. Although heteropaternal superfecundation is rarely observed among humans given its low frequency, in paternity disputes for dizygotic twins it is mandatory to demand the presence of the two twins in the testing to avoid wrong conclusions.

La superfecundación heteropaternal es un fenómeno extremadamente raro que se produce cuando un segundo óvulo, liberado durante el mismo ciclo menstrual, es fertilizado por un espermatozoide de un hombre diferente en relaciones sexuales separadas. En agosto de 2018, el Grupo de Genética de Poblaciones e Identificación de la Universidad Nacional de Colombia recibió una solicitud para establecer la paternidad mediante marcadores genéticos de un par de mellizos varones, en quienes se hizo el análisis del gen de amelogenina, el análisis de repeticiones cortas en tándem (Short Tandem Repeats, STR) autosómicas y del cromosoma Y (Y-STR) mediante kits comerciales de identificación humana y cálculos e interpretación del índice de paternidad y probabilidad de paternidad. Se obtuvo un índice de paternidad de 2,5134E+7 y una probabilidad de paternidad de 99,9999 % para el gemelo 2, en tanto que en el gemelo 1 se excluyeron 14 de los 17 marcadores del cromosoma Y y 14 de los 21 sistemas STR autosómicos evaluados. Los resultados indicaron que los gemelos tienen diferentes padres biológicos. A pesar de que la superfecundación heteropaternal rara vez se observa en humanos debido a su baja frecuencia, en las disputas de paternidad para los gemelos dicigóticos, es obligatorio exigir en la prueba la presencia de los dos gemelos para evitar conclusiones incorrectas.

Superfetation reduces the negative effects of pregnancy on the fast-start escape performance in live-bearing fish.

Superfetation, the ability to simultaneously carry multiple litters of different developmental stages in utero, is a reproductive strategy that evolved repeatedly in viviparous animal lineages. The evolution of superfetation is hypothesized to reduce the reproductive burden and, consequently, improve the locomotor performance of the female during pregnancy. Here, we apply new computer-vision-based techniques to study changes in body shape and three-dimensional fast-start escape performance during pregnancy in three live-bearing fishes (family Poeciliidae) that exhibit different levels of superfetation. We found that superfetation correlates with a reduced abdominal distension and a more slender female body shape just before parturition. We further found that body slenderness positively correlates with maximal speeds, curvature amplitude and curvature rate, implying that superfetation improves the fast-start escape performance. Collectively, our study suggests that superfetation may have evolved in performance-demanding (e.g. high flow or high predation) environments to reduce the locomotor cost of pregnancy.

Superfetation in the viviparous fish Heterandria formosa (Poeciliidae).

Heterandria formosa is a viviparous poeciliid native of the southeastern of United States of America. H. formosa exhibits unique reproductive features as: (a) production of extremely small eggs with scarce quantity of yolk (microlecithal eggs), (b) consequently, a high level of matrotrophy and development of a complex follicular placenta, (c) ovarian sperm storage that allows the continuous fertilization of oocytes and production of offspring and (d) development of high degree of superfetation. The degree of superfetation refers to the number of broods in different simultaneous stages of gestation. Morphological evidence of the degree of superfetation in H. formosa has not been documented. Therefore, and because of the general interest in the complex process of superfetation, the goal of this study is to morphologically define the degree of superfetation of H. formosa through two procedures: (a) histological analysis of entire ovaries in gestation and (b) dissection of visible embryos and the histological analysis of the remaining ovarian tissue. Results indicate that H. formosa can gestate up to seven broods at the same time.

Morphological structures for potential sperm storage in poeciliid fishes. Does superfetation matter?

Sperm storage within the female reproductive tract has been reported as a reproductive strategy in several species of vertebrates and invertebrates. However, the morphological structures that allow for sperm to be stored and kept viable for long periods are relatively unknown in osteichthyes. We use histological and stereological tools to identify and quantify sperm storage structures (spermathecae) in 12 species of viviparous Poeciliidae. We found spermathecae in nine species, six of which exhibit superfetation (the ability of females to simultaneously carry within the ovary two or more broods of embryos at different stages of development). These spermathecae are folds of ovarian tissue that close around spermatozoa. We compared the number and size (volume) of spermathecae between species with and without superfetation. Species that exhibit superfetation had a significantly higher number of spermathecae than species that do not exhibit this reproductive strategy. In addition, we found that the mean volume of spermathecae and total volume of spermathecae present in the ovary are marginally higher in species with superfetation. Our results contribute to the understanding of the morphological structures that allow for sperm storage in viviparous osteichthyes and suggest a positive relationship between superfetation and the capacity of females to store sperm.

Superfetation in live-bearing fishes is not always the result of a morphological constraint.

Superfetation is an unusual reproductive strategy that consists of the presence of multiple broods at different developmental stages within a single female. One hypothesis that was proposed to explain its adaptive significance suggests that, in fishes, superfetation is a response to selective pressures that promote a thin and streamlined body shape, such as high-velocity water systems. Superfetation may allow for reduction in ovary size and hence improve streamlining because superfetating females carry few large, full-term embryos at any given time. We tested this morphological constraint hypothesis using reproductive and morphological data from several populations of two viviparous fishes of the family Poeciliidae (Poeciliopsis gracilis and Poeciliopsis infans). We found no evidence to support the morphological constraint hypothesis. In both species the degree of superfetation varied as a function of a complex interaction between source population and female size, and this interpopulation variation was not associated with the velocity of the water current. Contrary to what we expected, females of P. gracilis with more streamlined bodies were observed in rivers where water velocity is slow or moderate. In P. infans the velocity of the water current did not predict variation in body shape. Our results are noteworthy because a previous study which focused on a congeneric species (Poeciliopsis turrubarensis) demonstrated strong support for this hypothesis. However, based on our evidence we conclude that the association among increased superfetation, streamlined morphologies, and fast-flowing environments is not a general rule and that the adaptive value of superfetation may differ among species.

A review of the mechanisms and evidence for typical and atypical twinning.

The mechanisms responsible for twinning and disorders of twin gestations have been the subject of considerable interest by physicians and scientists, and cases of atypical twinning have called for a reexamination of the fundamental theories invoked to explain twin gestations. This article presents a review of the literature focusing on twinning and atypical twinning with an emphasis on the phenomena of chimeric twins, phenotypically discordant monozygotic twins, mirror-image twins, polar body twins, complete hydatidiform mole with a coexistent twin, vanishing twins, fetus papyraceus, fetus in fetu, superfetation, and superfecundation. The traditional models attributing monozygotic twinning to a fission event, and more recent models describing monozygotic twinning as a fusion event, are critically reviewed. Ethical restrictions on scientific experimentation with human embryos and the rarity of cases of atypical twinning have limited opportunities to elucidate the exact mechanisms by which these phenomena occur. Refinements in the modeling of early embryonic development in twin pregnancies may have significant clinical implications. The article includes a series of figures to illustrate the phenomena described.

Comparative life histories of fishes in the subgenus Limia (Pisces: Poeciliidae).

This study presents life-history descriptions for 12 species in the subgenus Limia, which are endemic to the Greater Antilles. All species in this study lack evidence of superfoetation, producing a single brood of offspring before developing subsequent broods. Interbrood intervals (number of days between parturition events) are also consistent with intervals of species that lack superfoetation. Maternal provisioning, characterized by matrotrophy index, is <1.0 for all species of Limia. This is consistent with species that provide little or no maternal provisioning to developing embryos after ovum fertilization (lecithotrophic). Four species exhibit potentially bi-modal size distributions of mature males. Work on other poeciliids suggests that such bimodal distributions can be caused by genetic polymorphisms in some species. Principle component analyses revealed an axis of interspecific variation in life histories that separated species with small size at maturity and the production of many, small offspring from those with large size at maturity and that produce few, large offspring. This pattern of life-history diversity occurs in many other groups of organisms.

Comparative life histories of fishes in the genus Phallichthys (Pisces: Poeciliidae).

This study presents a description of the life histories of all four species of the genus Phallichthys, found primarily in the Atlantic slope of Central America (ranging from northern Panama to Mexico), based on a combination of data collected from preserved and living specimens. All species produced a single litter of offspring before developing another brood (i.e. no superfoetation). In the laboratory, the mean time interval between successive litters ranged from 24 to 48 days, further suggesting that they lack superfoetation. Embryos lose from 15 to 65% of their dry mass during development, meaning all or the large majority of resources required for development are provided prior to fertilization (lecithotrophy). All mature male size distributions were platykurtotic and appeared either bimodal or multimodal. Multimodal and skewed size distributions have been associated with genetic polymorphisms for size at maturity in other species of Poeciliidae. As the sister clade to Phallichthys includes genera in which all species have superfoetation (Neoheterandria and Poeciliopsis), these results suggest that their common ancestor with Phallichthys also had superfoetation and that the trait has been lost.

Unpredicted ovulations and conceptions during early pregnancy: an explanatory mechanism of human superfetation.

In this bioessay, a literature review on human superfetation was performed in order to find epidemiological variables associated with this phenomenon. Thereafter, an explanatory mechanism of superfetation compatible with the endocrinological, histological and physiological changes undergone by women during early pregnancy is proposed. Superfetation can be defined as the ovulation, fertilisation and implantation of a second or additional embryo(s) during pregnancy. The literature review evidences a small discordance in gestational age between dizygotic twins in humans (range: 2-4 weeks; mean ± s.e.m.: 3.3 ± 0.3 weeks). This difference is compatible with a luteal out-of-phase (LOOP; i.e. atypical increase in E2 levels in the mid-luteal phase)-like event occurring between 1 and 3 weeks after the ovulation that allowed the first pregnancy to take place. The LOOP-like event may allow passive sperm transport from the vaginal fornix to the Fallopian tube ipsilateral to the ovulatory ovary and trigger a LH peak and ovulation. Furthermore, during very early pregnancy, the decidual reaction is not yet completed and at least one proximal Fallopian ostium may be opened, allowing the passage of the spermatozoa ascending to the fertilisation site and the extra embryo(s) descending to the implantation site(s).

The concept of superfetation: a critical review on a 'myth' in mammalian reproduction.

Superfetation is understood as another conception during an already ongoing pregnancy. This implies the existence of young of different developmental stages within the female reproductive tract during certain periods of pregnancy. Nevertheless, a clear definition of the term as well as distinct criteria to identify the occurrence of superfetation in a species is missing. The variable anatomy of mammalian reproductive tracts seems to make the occurrence of superfetation more or less likely but impedes the simple evaluation of whether it is present or not. Additionally, adequate determination methods are missing or are difficult to apply at the right time. Superfetation or rather superfetation-like pregnancies are reported for numerous species including humans, livestock and rodents. The usual criteria to assume a case of superfetation include the finding of discordantly developed young within the uterus during post mortem or parturition of young after a birth interval shorter than the assumed pregnancy length. Often the occurrence of superfetation is concluded because other explanations of reproductive artifacts are missing. Even severe reproductive pathologies are often confused with superfetation. True superfetation or superfetation as a reproductive strategy may exist in some mammals. In the American mink (Neovison (Mustela) vison) and the European badger (Meles meles) superfetation occurs in combination with embryonic diapause. In the European brown hare (Lepus europaeus), superfetation has long been assumed to exist but evidence is still controversial. Superfetation definitely occurs in certain species of poeciliid and zenarchopterid fish, some of which also exhibit viviparity and maternal care. In mammals, the evolution of such a reproductive mechanism poses many interesting evolutionary, endocrine, microbial and immunological questions that require further investigation. Here we review the scant and at times ancient literature on this poorly understood topic. The different manifestations of superfetation are defined and reliable criteria to detect superfetation are outlined. Also, the differentiation of superfetation into a reproductive strategy or as a disrupted, abnormal reproductive function is discussed. Due to the different discussed functional aspects of superfetation, it is appropriate to establish a more detailed scheme to classify the true natural superfetation cases into superfertilization, superconception and superfetation proper. To date, there is no mammal species known for which superfetation proper in terms of finding discordantly developed fetuses has been conclusively demonstrated to be not only a rare occurence but an evolved reproductive strategy.

Superfetation after ovulation induction and intrauterine insemination performed during an unknown ectopic pregnancy.

This report describes the first case of superfetation after ovarian stimulation with gonadotrophins and intrauterine insemination (IUI) that were performed in the presence of an undiagnosed tubal pregnancy. A 32-year-old woman who underwent repeated attempts of ovarian stimulation and IUI was hospitalized for severe pelvic pain and submitted to laparoscopic salpingectomy because of ruptured salpynx containing a 6-week pregnancy. Transvaginal ultrasound examination showed a simultaneous intrauterine 2-week pregnancy that had been conceived by ovarian stimulation and IUI while the tubal pregnancy was already ongoing and still undiagnosed. The intrauterine pregnancy went on until term and ended with the spontaneous delivery of a healthy baby. This report demonstrates that human superfetation may occur after gonadotrophin treatment and IUI in the presence of an ongoing tubal pregnancy. It is recommended to perform a pregnancy test before starting ovulation induction even when an apparently normal blood discharge appeared.

[Superfetation: case report and review of the literature]. / Superfoetation: à propos d'un cas et revue de la littérature.

We report the case of a dichorionic-diamniotic pregnancy in which a discordance in the size of the fetuses was observed as early as the first trimester. This discordance in size was maintained over time and the two fetuses continued their respective growths. We suggest the very rare phenomenon of superfetation as a diagnosis because less than 10 cases are described in the literature. Even though a formal proof of the diagnosis is difficult to obtain, the elements described in this article rally in favor of this hypothesis. Superfetation is defined by the fertilization and the implantation of a second oocyte in a uterus already containing the product of a previous conception. After a description of the case, a review of the literature enables us to describe the frequency, the possible risk factors and the existing case reports on the subject. The rarity of this case justifies its publication for the information of clinicians.

[Superfecundation and superfetation--the forgotten entities].

Superfecundation and superfetation are rare and obscure phenomena with no clear clinical significance but with legal and moral-social meanings. These obstetric rarities are known since the times of the ancient Greeks. There are several physiological explanations that account for superfecundation but not for superfetation, yet, both have been described. In this era of assisted reproductive techniques it is reasonable to assume that the prevalence of superfecundation increases, which may also apply to superfetation. Today, there are several reliable diagnostic techniques to verify heteropaternity in multifetal pregnancies, hence superfecundation. Nevertheless, our knowledge regarding these amazing phenomena remains limited due to both ethical and medico-legal barriers that prevent their implementation.

Discordant twins with the smaller baby appropriate for gestational age--unusual manifestation of superfoetation: a case report.

BACKGROUND: Documentation of superfoetation is extremely rare in humans., The younger foetus has invariably been small for gestational age (estimated from the date of the last menstrual bleed) in all the cases reported in the literature. We report a case where the younger twin was of appropriate size for gestation. CASE PRESENTATION: The first of twins was of 32 weeks gestation and the baby was of appropriate size and development for the gestational age. The second twin was of 36 weeks gestation. Gestational age was estimated with the New Ballard score, x-ray of the lower limbs, dental age on x-ray, and ophthalmic examination. CONCLUSION: Bleeding on implantation of the first foetus probably helped demarcate the two pregnancies. Dental age and the New Ballard score can be used to diagnose superfoetation in discordant twins, when detailed first trimester ultra-sound data is not available.