Conjoined Twins: Historical Perspective and Report of a Case

By Kokcu, Arif; Cetinkaya, Mehmet B; Aydin, Oguz; Tosun, Migraci


In this article we review the historically important cases of conjoined twins (Biddenden Maids, Siamese twins, Blazek sisters) and contemporary knowledge regarding incidence, etiopathogenesis, antenatal diagnosis, antenatal management, and outcome of conjoined twins. We also present a case of male cephalothoracoomphalopagus, which is extremely rare.

Keywords: Biddenden maids, Siamese twins, Blazek sisters, cephalothoracoomphalopagus

A historical review of conjoined twins

In classical times, gross anomalies were considered a warning from the Gods. St. Augustine took the view that they were a reminder from God of man’s imperfection and original sin. Scholars, including Aristotle, Hippocrates, Empedocles, and Pliny the Elder, thought that the unborn child was susceptible to external stimuli. Such extrinsic factors were blamed when a case of craniopagus twins were born in sixteenth century Germany. Apparently, the pregnant mother clashed heads with a neighbor [I].

Artistic representations of the human body date back 15 000 years. From this earliest period of art itself, the ill and the deformed were portrayed almost as often as the healthy and vigorous. Given the superstition and fear that must have accompanied conjoined births – and their rarity – it would come as no surprise if such births had never been portrayed. Nevertheless, excavations of Tlatilco, a small Mexican village that existed about 3000 years ago, have revealed remarkably accurate clay sculptures of a wide range of facial and cranial duplications. Many of these artifacts are small female figurines with small waists and breasts, short phocomelic arms, and bulging thighs. Although most of the figurines have normal faces, some have double faces with a shared, central, cyclopic eye and normal lateral eyes. Others have separate faces, and a few are fully dicephalic (double headed) with separate necks on a single body [2]. Tlatilco was part of the Olmec cultural world, sharing its maize agriculture, iconography, and much else from that widespread society. However, these small diprosopus (partial facial duplication) and dicephalic statues appear only at Tlatilco and nowhere else in Olmec art. Although representations of ‘monstrous’ beings are common in all traditional iconography, the faces and heads from Tlatilco are interesting because they are developmentally and proportionately correct-they are not just impossible hybrids, such as centaurs. The reports of unexplained clusters of conjoined- twin births around the world make the biologic accuracy of these Tlatilco figures particularly tantalizing [2].

Since ancient times, the entity of conjoined twins has fascinated both lay and medical people alike. Anecdotal reports of viable conjoined twins in European medical history date back more than 1000 years. According to tradition, the Biddenden Maids, Mary and Eliza Chulkhurst, were born to fairly wealthy parents in the year AD 1100. Their bodies were joined at the hips and shoulders. They were naturally very close friends, although they sometimes disagreed in minor matters, and had “frequent quarrels, which sometimes terminated in blows”. In AD 1134, when the Maids had lived joined together for 34 years, Mary was suddenly taken ill and died. It was proposed that Eliza should be separated from her sister’s corpse by means of a surgical operation, but she refused with the words “As we came together we will also go together”, and herself died six hours later. In their will, the Maids left certain parcels of land in Biddenden, containing in all about 20 acres, to the church wardens of that parish; the annual rent from the fields, which is stated to have been 6 guineas at the time of the Maids’ death, was to provide an annual dole for the poor. In 1808, the income from the Maids’ lands had increased to 31 guineas and 11 shillings per annum. While the Biddenden Maids have been extensively cited in the teratological literature as one of the earliest genuine cases of conjoined twins upon record, some antiquaries have considered the tradition to be wholly fabulous [3].

There is a remarkable accumulation of reports of English conjoined twins at the beginning of the 12th century. According to Lycosthenes’ Chronicon Prodigorum et Ostentorum from 1557, conjoined twin brothers had been born in England in 1112, and their bodies were joined at the hips and “ad superiores panes”, like in the popular descriptions of the Biddenden Maids. Even more interesting is that a medieval historical chronicle, the Chronicon Scotornm, tells us that in AD 1099, a woman gave birth to “two children together, in this year, and they had but one body from the breast to the navel, and they were two girls”. In the Irish chronicle Annals of the Four Masters is an almost identical description, although the conjoined twin girls are stated as having been born in 1103; in the Annals of Clonmacnoise their year of birth is given as AD 1100. These ancient descriptions are unreliable in detail and probably dependent on each other, but in spite of this, they add some credibility to the old tradition that the Biddenden Maids were really born in AD 1100 [3].

The first well-known case was not documented until 1811, when two boys – Chang and Eng – were born in Bangkok, Thailand, attached to each other at the sternum. P.T. Barnum named them the “Siamese twins”. As they traveled the world with Barnum’s circus, they consulted a multitude of physicians. All, including Rudolf Vircow, concluded that separation would be fatal to both. This prognosis may have been welcomed by the twins because their wealth and fame depended on their conjoined state. At the age of 31, these xiphopagus twins married two sisters who bore them a total of 21 children; they died within hours of each other at the age of 61. An autopsy found that they shared no organs. They only shared a small amount of liver tissue, peritoneum, and the hypogastric artery and vein. Death probably came to the surviving twin not from fright, as initially stated, but from slow exsanguination as blood flowing into the already dead twin was not returned [2,4-6].

A young couple prepared for the birth of their second child – the Blazeks were a middle-class Bohemian farming family who lived in the tiny village of Skrejsov in the central part of the present-day Czech Republic. The expectant mother was 22 years old, and the father-to-be was 38 years old. The delivery was vaginal and began simply. Rosa and Josepha Blazek were born in Bohemia on January 20, 1878, as pygopagus twins, Rosa being the first such twin to a mother having a normal infant. Word quickly spread throughout Bohemia of these unusual sisters. Even as toddlers, the Blazek sisters were exhibited in local village fairs “doing their duty on a single potty”. They began to walk in the second year and could speak by age 4 years. Their schooling was considered normal instruction by contemporary standards and was overseen by home-teachers. They learned to play the violin at a young age. Menarche occurred simultaneously for both girls, one month before their 14th birthday [4,5,7].

The Blazek case exemplifies an extreme manifestation of the terminal monogenital pygopagus type of conjoined twins. Their pelves and sacrum were united at the lower posterior part, although the vertebral columns were not parallel. In the genital region, the sisters’ degree of fusion was maximal. The sisters shared an anus that was situated in a common anal groove formed by the two buttocks on which the sisters lay. A common urethral ostium existed in the midline immediately dorsal to the single clitoris and labia minora. Beneath the shared urethral ostium was the vagina, which appeared to develop as an asymmetric fusion of two separate vaginas separated by a nearly continuous longitudinal membrane 0.75 cm thick. These two distinct vaginas communicated proximally with two normal-sized but separate uteri. Each uterus had two fallopian tubes, and the ovarian anatomy was normal [7].

The sisters claimed to have sexual intercourse only once, on July 20, 1Q09. Both sisters agreed to coitus, and both achieved orgasm. Intercourse involved the vagina of Rosa only, and her last menses before pregnancy occurred in mid-July 1909. Interestingly, Josepha continued to menstruate from her side of their shared vagina throughout Rosa’s pregnancy and until approximately gestational week 32. A healthy male infant was delivered vaginally on April 16, 1910 [7]. From 1910 through 1922, the Blazek sisters continued their worldwide circuit of exhibition travel, and no records exist to describe their medical care during this period. In early 1922, however, their touring was unexpectedly interrupted in Chicago when Rosa became ill with a serious cough. This soon developed into influenza, and Rosa’s convalescence required three weeks. Josepha then experienced abdominal pain and jaundice that was thought to be appendicitis. With a differential diagnosis including cholecystitis, the sisters were admitted to the West End Hospital of Chicago on March 25, 1922, under the care of Dr Benjamin Breakstone [7]. The sisters’ temperatures and pulse rates rose, although Josepha’s were consistently higher than Rosa’s. As Josepha’s condition steadily deteriorated, the notion of performing surgery to separate the twins was considered to save \Rosa’s life. However, before an operation plan could be developed, Josepha became comatose. Within 24 hours, Rosa was also unresponsive. Pulmonary compromise worsened in both, and this quickly advanced to “terminal bronchopneumonia”. On March 30, 1922, five days after hospitalization, Josepha died. The death of Rosa quietly followed 12 minutes later. Their age at death was 43 years [7].

Autopsy of the Blazek sisters was performed on April 2, 1922. Dissection revealed situs inversus that involved Rosa’s liver (a condition not suspected before death). Furthermore, the forensic investigations verified independent abdominal cavities for the sisters; no vascular communication between aortas of inferior venae cavae could be found. Any vascular anastomoses that existed between the sisters must have involved only the iliac vessels or their branches. This limited vascular connection may help explain the reason why selected endocrine mediators or toxins of sufficient bioactivity or half-life could manifest their effects in both sisters [7].

A further difficulty in accepting the tradition of the Biddenden Maids as entirely authentic is the nature of their malformation: in the available plates and drawings, they are depicted as being conjoined at both the shoulders and the hips. It is most uncommon that Siamese twins have two separate parts of conjunction, and very few such cases have been reported; most teratologists would not accept the possibility of a fusion at the hips and shoulders. In 1895, the teratologist J.W. Ballantyne was the first to consider the Biddenden Maids from a teratological point of view. He suggested that they were in fact only conjoined at the hips and thus belonged to the teratological type pygopagus. In such conjoined twins, each has two arms and two legs, and it has often been noted that in order to walk without difficulty, they put their arms around each other’s shoulders. About 18% of conjoined twins are of the pygopagus teratological type, where twins are joined at the sacrum. The twins have more or less complete fusion of the rectum and other perineal structures, but the spinal cords are usually separate. The first successful surgical separation of pygopagus twins was performed in 1950 [3].

The Hungarian sisters, Helena and Judith, were a celebrated pair of pygopagus conjoined twins in the 18th century; they traveled extensively through Europe, and were examined by many eminent naturalists. In later life, the Hungarian sisters entered a convent, where they died aged 22 years in 1723 [3].


Conjoined twins are regarded as an ‘extraordinary accident of nature’. The exact frequency of conjoined twins is not established, and the estimated incidence varies in the literature. All conjoined twins are monoamniotic, monochorionic, monozygotic twins. Spontaneous twinning occurs in 1.6% of all human pregnancies, of which 1.2% are dizygotic and 0.4% are monozygotic. Monochorionicmonoamniotic twins account for less than 1% of monozygotic twins, and conjoined twins are even less common, occurring in approximately 1 in 50 000100 000 and 1:600 twin births. Conjoined twinning is three times more common in female fetuses than in males. It is believed that 1 in 40 monozygous twins fails to separate completely, yielding united or conjoined twins. Throughout the years, there have been more than 1000 reports concerning conjoined twins. It has been reported that the incidence of conjoined twins does not vary with maternal age, parity, or race, while the recurrence risk seems to be negligible. In addition to this, the frequency is reported as 1:14 000 births in India and Africa and 1:250 000 live births in Europe and the USA, suggesting an increased incidence in black populations [4,7-14].


Conjoined twins are classified on the basis of the most prominent site of union together with the suffix pagus, which means fixed. Ventral unions occur 87% of the time and are classified as: cephalopagus (11%), thoracopagus (19%), omphalopagus (18%), ischiopagus (11%), and parapagus (28%). Dorsal unions occur in 13% of conjoined twins and are classified as: craniopagus (5%), rachiopagus (2%), and pygopagus (6%).


Fusing from the top of the head down to the umbilicus. There are two faces on opposite sides of the conjoined head. The lower abdomen and pelvis are not united, and there are four arms and four legs.


United face to face from the upper thorax down to the umbilicus. The union always involves the heart. The pelvises are not conjoined, and there are four arms and four legs.


Fetuses are joined face to face, primarily in the area of the umbilicus. The union often includes the inferior lower thorax but never the heart or single patent intercardiac vessel. The pelvises are not united, and there are four arms and four legs.


United from umbilicus down to a large conjoined pelvis with two sacrums and two symphises pubis. There are four arms and four legs, and the external genitalia and anus are always involved.


Parallel duplication of two notochords in close proximity will produce twins conjoined laterally. They are always joined anterolaterally, pulled together ventrally by closure of the umbilicus, and are always single at the caudal end but double at the cranial end [6,8,10,12,15].


United on any portion of the skull except the face and foramen magnum. The trunks are not united, and there are four arms and four legs.


Fused above the sacrum; the union may involve occiput as well as vertebral column.


Share the sacrococcygeal and perineal regions, usually one anus with two rectums, four arms, and four legs.


Conjoined twinning is an extremely rare complication of monozygotic twins that results from incomplete embryonic division occurring between 13 and 15 days after conception. Conjoined twins occur if twinning is initiated after the embryonic disc and rudimentary amniotic sac have been formed. Because conjoined twins develop after differentiation of the chorion and amnion, all conjoined twins are monochorionic-monoamniotic [10,12].

The precise etiology of conjoined twinning is unknown. In the 18th century, it was believed that conjoined twins were produced when one ovum was fertilized by two sperms (collision theory). Currently, two important theories have been proposed to account for the formation of conjoined twins. The most common explanation is an incomplete fission of a single zygote or, alternatively fusion of two dizygotic or monozygotic embryos in their very early embryonic development. On the basis of this explanation, routine cytogenetic analysis of all conjoined twins, including teratomas, has been recommended. Although it is based on molecular evidence, this theory has been critically challenged. Molecular analysis with informative genetic markers has been performed and no genetic difference between the autosite and parasitic fetus was found. These data are consistent with monozygous (parasitic) conjoined twins. Other authors have hypothesized that the proximity of the ovum and its first polar body after dispermic fertilization may cause a parasitic conjoined twin of dissimilar sex [4,8,9,13,16,17].

Assisted reproductive technologies (ART) are extensively used worldwide, producing an increasing number of high-order multiple gestations, which continue to pose a considerable management challenge to clinicians. The phenomenon of increased rates of monozygotic twinning after ART has been found in all types of ART, including conventional in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI), blastocyst culture, and assisted hatching. The incidence has been recorded as 1.35% of all ART pregnancies, or two to eight times more common than in the general population. The rarity of conjoined twins precludes any statistical analysis of the relative risk of its happening after ART, but it seems reasonable to consider that this type of twinning would be more likely to occur after ART than in the general population. The combination of ICSI and conjoined twins has also been reported [13].

It may coincide with X chromosome inactivation, implying that lionization may be a driving force for female monozygotic twins. For this reason, the excess of females among monozygotic twins is most marked among conjoined twins. More than 70% of all conjoined twins are female. The nine sets in Rudolph et al. [18] were all female. In addition to this, the sexes of the cephalothoracopagus conjoined twins presented by Wedberg et al. [5] in 1979 and Turgut et al. [9] in 1998 were female. Zeng et al. [19] reported that genetic or environmental factors other than abnormal X-inactivation must be involved in causing monozygous multiple gestation or conjoined twins. Steinman [20] reported that a significant number of the women who delivered conjoined twins were subjected to environmental triggers. Of particular interest is increased conjoined twinning following the use of oral contraceptives. The incidence of uniovular twinning is inversely related to a woman’s prepregnancy weight. It is hypothesized that this resulted from prolonged ovulatory dysfunction in underweight women. It has been reported that factors that induce calcium depression and delayed implantation encourage uniovular duplication in general and conjoined twinning in particular [2O].


Ultrasound has become the safest and most reliable way to make this diagnosis in utero. Prenatal diagnosis has increasingly been reported for conjoined twins since the first report in the late 1970s. The diagnosis of conjoined twins can be made by ultrasound in the first trimester. At this early gestational age, the diagnosis should be suspected if the embryonic pole appears bifid. However, the diagnosis should be made with caution in the first trimester and, when suspected, follow-up imaging should be performed to con\firm the diagnosis. Additional sonographic features of conjoined twins that may be apparent in the first and second trimesters include an inability to separate the fetal bodies and skin contours, lack of a separating membrane between the twins, the presence of more than three vessels in the umbilical cord, heads remaining at the same level and body plane, extremities in unusual proximity, and failure of the fetuses to change their relative positions over time. Polyhydramnios is found in approximately 50-76% of cases, but usually not in the first trimester. Duplication of any anatomical parts and persistence of the inseparable parts on repeated scans confirms the diagnosis. The evaluation of conjoined twins should include a detailed ultrasound examination, including a fetal echocardiogram, at 18-20 weeks to determine the extent of shared organs and to exclude additional anomalies. Associated anomalies, even in organs unrelated to the conjoining, are not uncommon. Further information may be gained by magnetic resonance imaging (MRI) evaluation. A diagnosis of the anatomy of shared organs and the presence of additional malformations is essential for counseling families regarding outcome and planning postnatal surgical separation. Because chromosomal abnormalities are rare in conjoined twins, karyotyping is generally not indicated [4,6,8,10,21].

Although two-dimensional (2D) ultrasound is instrumental in prenatally diagnosing conjoined twins, precise classification is difficult because of complex three-dimensional (3D) structures. 3D ultrasound has shown promise in improving the visualization of complex anatomic spatial relationships. It may therefore be beneficial in defining the complex fetal anatomy of conjoined twins, whereby early diagnosis facilitates selective termination [U]. 3D ultrasound has the potential to add anatomic information and it is valuable to improve the classification accuracy. The category of conjoined twin is already suspected by 2D scanning, only to be confirmed by 3D ultrasound. In cases of conjoined twins, the majority of parents opt for a termination irrespective of the site of twin attachment. Within this context, the additional value of 3D scanning seems further limited to those cases for which the parents opt for a conservative prenatal management

and postnatal surgery. In these cases, the 3D ultrasound examination must be postponed to after 14 weeks of gestation when better views of the anatomy can be obtained. However, it is likely that other imaging techniques such as MRI will provide more accurate and valuable information for prenatal counseling and the planning of postnatal surgery than second trimester 3D ultrasound [14].


A thorough targeted ultrasound examination, including a careful evaluation of the point of connection and the organs involved, is essential before counseling is provided. Surgical separation of nearly complete conjoined twins may be successful when organs essential for life are not shared. Color Doppler and 3D ultrasound can be effectively used to complement 2D imaging, to confirm the diagnosis as well as to determine the extent of organ sharing and definite classification of conjoined twinning. 3D sonography also provides images that are easier for parents to understand, which can help them with decision-making. Since fetal soft tissues are so well visualized with today’s sonographic equipment, invasive imaging procedures such as amniography should no longer be necessary. Consultation with a pdiatrie surgeon often facilitates parental decisionmaking [4,6,22-25].


Survival of conjoined twins depends largely on the site of conjoining and the organs involved. In a series of 14 cases of prenatally diagnosed conjoined twins, 28% of cases died in utero, 54% died immediately after birth, and only 18% survived. Emergent surgical separation is performed in the event that one twin dies, or if a life-threatening condition exists in one of the twins that threatens the life of the cotwin. In these cases, the survival rate is reported as 30-50%. Elective separation, which usually occurs at 2-4 months of age, allows for stabilization of the twins, confirmation of anatomic relationships, diagnosis of previously unrecognized anomalies, and adequate planning of surgery. Most series report a survival rate of 80-90% for elective separation [1O].

Overall, the prognosis depends on the type of fusion and presence of associated structural defects. In early pregnancy, the parents can opt for a medical or surgical termination. After 18-20 weeks, transvaginal termination will become difficult and the delivery could require a major surgical procedure, that is, hysterotomy or classical cesarean section [14].

If they are considered to have a poor chance of surviving and are small enough to pass through the birth canal without damaging the mother, vaginal delivery may be the preferable option. It is suggested that with near-term-sized twins, cesarean delivery seems indicated even if the fetuses are dead [4,26,27].

Our case. A very rarely seen case of conjoined twins: Cephalothoracoomphalopagus

A 27-year old, multigravid woman (gravida 4, para 3, alive 2) was referred to Ondokuz Mayis University Hospital at the 34th gestational week. There was no history of exposure to teratogenic agents in pregnancy. She had not consulted any gynecologist before applying to our clinic. During abdominal ultrasonography, a fetus, with four legs, four arms, a single head, single thorax, two hearts (one of which was atretic), and double vertebra was seen. The biparietal diameter measurement was consistent with 32 gestational weeks. The amount of amniotic fluid was normal. According to these ultrasound findings, a cephalothoracopagus conjoined twin was diagnosed. Of the history of the patient, we learned that in her first pregnancy fetal ventriculomegaly was diagnosed and her pregnancy resulted in fetal death at 24 weeks of gestation. Her second and third pregnancies resulted in the births of normal live children. There was also no family history of twinning. The couple was informed that this was a surgically inseparable condition and opted for pregnancy termination. Since the pregnancy was advanced, and considering that conjoined twins may cause a genital trauma, the delivery was performed by cesarean section. Conjoined twins with one head, one body, four arms, four legs, Apgar score 1, weighing 3520 g were delivered (Figures 1 and 2). The conjoined twins died twenty minutes following delivery.

Figure 1. Postmortem photograph demonstrating anterior aspects of cephalothoracoomphalopagus conjoined twins.

After delivery, in external examination of the conjoined twins, it was seen that the twins were joined from the head down to the umbilicus with the presence of one head, one neck, a single thorax, a single upper abdomen, and a single umbilical cord. This appearance was consistent with cephalothoracoomphalopagus. The head and face were just in the middle of conjoined thorax. They had two eyes, one mouth, one nose and two ears. On the thorax, at the front and at the back, there existed a total of four nipples, being two at either side. The upper and the lower extremities were of normal morphology and in appropriate locations at the front and at the back. They had male external genitalia (Figure 1).

In the postmortem autopsy examination, it was found that the upper part of the body from the umbilicus level was single, excluding the extremities. The neck was single but the brain stem and spinal cord were double. At the base of the skull there were two foramina magna with normal spinal cords. There were two cerebral hemispheres with normal lateral ventricles divided by falx cerebri in the supratentorial compartment, but there were two posterior cranial fossa including four cerebellar hemispheres and brain stems. Each twin had normal cervical, thoracic and lumbar spine. There was a thymus, two hearts one of which was atretic, and left and right lungs. Larynx, trachea, esophagus, stomach and duodenum were present and all single. There was a single liver and a single pancreas, two spleens, but the small intestine and colon, found in the both abdomens, were conjoined. There was a single umbilical cord that had four vessels (two arteries and two veins). There were two kidneys, two ureters and two bladders. The karyotype of the conjoined twins was found out to be 46XY.

Figure 2. Postmortem photograph demonstrating posterior aspects of cophalothoracoomphalopagus conjoined twins.

As far as we are aware, this case is the first of cephalothoracoomphalopagus twins of male sex. In the autopsy examination of the conjoined twins, a normal cerebrum consisting of two hemispheres and two cerebral peduncles was seen, and two brain stems joined at the cranial end of the midbrain. Neuropathologic features have shown a resemblance to the findings of the cephalothoracopagus case presented by Turgut et al. [9]. To the best of our knowledge, this is the second case in which such neuropathologic features in this type of conjoined twins have been determined.

Cases of conjoined twins occur so rarely that it is important to leam as much as possible from each case.


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1 Department of Obstetrics and Gynecology, School of Medicine, University of Ondokuz Mayis, Satnsun, Turkey and

2 Department of Pathology, School of Medicine, University of Ondokuz Mayis, Samsun, Turkey

(Received 14 April 2006; revised 7 June 2006; accepted 29 November 2006)

Correspondence: Arif Kokcu, Bahcelievler mah, Abdiilhakhamid Cad, Onursal Ap. No. 19/4, 55070 Samsun, Turkey. Tel: +90 0362 4576000 ext. 2452. Fax: +9 0362 4576029. E-mail: arifkokcu

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