Year : 2021 Month : April Volume : 8 Issue : 14 Page : 925-931.

Sirenomelia - Mermaids Out of the Sea – Report of 3 Cases from Kerala, India, with Review of Literature

Sherin Daniel1, Prema Nilakantan Unni Sumathy2, Krishna Balachandran Nair3, Santha Sadasivan4

1 Department of Pathology, Christian Medical College, Vellore, Tamil Nadu, India.
2 Department of Pathology, Government Medical College, Parippally, Kollam, Kerala, India.
3 Department of Pathology, Government Medical College, Trivandrum, Kerala, India.
4 Department of Pathology, Sree Mookambika Institute of Medical Sciences, Kanniyakumari, India.


Dr. Sherin Daniel, Assistant Professor, Department of Pathology, 4th Floor, ASHA Building, Christian Medical College, Vellore-632004, Tamilnadu, India.
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Sirenomelia or mermaid syndrome is a rare and fatal congenital multisystemic anomaly characterised by different degrees of fusion of lower limbs, thoracolumbar spinal anomalies, sacrococcygeal agenesis, genitourinary and anorectal atresia. It is more common in foetuses of diabetic mothers and monozygotic twins. Approximately 300 cases have been reported in the literature and very few have been reported from this subcontinent. Although, this syndrome is incompatible with life due to the association of several congenital visceral abnormalities, there have been nearly nine reported sirenomelia affected cases, who have survived after multiple reconstructive surgeries. The most important factor for survival of affected new-borns was functional kidney.



All foetal autopsy cases received over the past 5 years in the Department of Pathology, Trivandrum Government Medical College were analysed with special emphasis on sirenomelia (mermaid syndrome). The clinical history, post-mortem x-ray, and gross evaluation of these sirenomelia babies were studied in detail.



There were 3 cases of sirenomelia out of 14 cases associated with syndromes during the study period. The cases encountered had various known risk factors and different degrees of lower limb fusion, as mentioned in the literature.



Congenital anomalies are on the rise as a cause of fetal death. Fetal autopsy correlates well with prenatal ultrasound and karyotyping. It provides added information in a significant number of cases. Sirenomelia is a rare congenital anomaly where early detection by prenatal ultrasound will help in timely management of pregnancy. Genetic & prenatal diagnosis would ensure an optimal management from psychological and health cost point of view. This case series emphasises the need for perinatal autopsy for all cases of foetal death.



Foetal Autopsy, Sirenomelia, Mermaid Syndrome, Caudal Regression Syndrome


The study of the dead enriches the knowledge of life and death, which can be accomplished by autopsy. Autopsies in general have their roots from the end of the thirteenth century.1 The approach to perinatal autopsy is not the same as in adult autopsy.2 The diseases and conditions considered in the foetus are not the same as that encountered in adults. The perinatal autopsy is a multidisciplinary effort involving the obstetrician, radiologist, pathologist, paediatrician and a geneticist.3 The pathologist in general, has a growing responsibility of documenting and reporting anomalies for genetic counselling, providing epidemiological data and stimulate research. Several studies have been conducted worldwide including India. Such studies were conducted to provide valuable information about the frequency and distribution of congenital anomalies and important clues to the early diagnosis, prevention and treatment. Autopsy facilities are still primitive in India1. This study focuses on one such rare congenital malformative disorder seen in foetuses called sirenomelia. This disorder is extremely rare and often fatal,4 with an incidence of about 1 in 100,000 pregnancies.5 This disorder is also known as the mermaid syndrome which was described by Rocheus in 1542.6 The most characteristic yet inconstant feature of this malformative disorder is the complete or partial fusion of the lower limbs into a single lower limb.7 The infant bears a resemblance to the mermaid of ancient Greek mythology.8

Around 300 cases have been reported in the world literature, of which only 13 have been from India. We hereby report three cases of sirenomelia that were received in the department in five years. This case series is one of the largest in Indian literature. This was undertaken with a view to study the incidence of congenital malformations in perinatal death in general, analyse the utility of histopathology in the cause of death, discuss the findings in relation to the present literature and related controversies of its etiopathogenesis.



To find out the incidence of congenital anomalies detected in perinatal autopsies, to study in detail about sirenomelia (mermaid syndrome) babies with respect to the risk factors, the various anomalies present in them and their outcome.


This was a retrospective descriptive study where all foetal autopsy specimens received in the Department of Pathology, Government Medical College, Trivandrum over a period of five years from January 2009 to December 2013 were analysed. The cases of sirenomelia babies received during this study period were studied in detail. Relevant clinical history and post-mortem x-rays were obtained. The specimens were grossed according to the standard autopsy protocols, haematoxylin & eosin stained tissue sections were studied and a detailed literature review was done.


Of the 440 fetal autopsies received in the department during the study period, 23.4 % of cases (103 cases) had congenital anomalies [Table 1]. Most of the cases had multiple anomalies involving different organs (38 / 103 cases). On further analysis, the most common system to be involved was the gastrointestinal tract followed by cardiovascular system and genitourinary system. There were 14 cases associated with syndromes, among them sirenomelia (mermaid syndrome) was seen in 3 cases.



Case 1

A 32-year-old healthy multigravida lady with monochorionic monoamniotic (MCMA) twins at 30 weeks + 1 day of gestational age was referred to our institute with history of preterm labour pains. She had a normal antenatal course with an ultrasound scan done two months ago revealing MCMA twin gestation (one cephalic and the other in breech presentation). Her oral glucose tolerance test (OGTT) was abnormal. She had a previous normal delivery, and the child was healthy. There was no history of drug intake, radiation exposure or history of maternal diabetes mellitus. On admission, her vitals were stable. On examination, she was found to be in second stage of labour with uterine size of 34 - 36 weeks, had mild contractions and good fetal heart sounds. Her routine blood investigations were normal. Ultrasound scan on admission showed MCMA twin fetuses. The 1st fetus had an estimated gestational age of 29 weeks + 1 day with cephalic presentation and an estimated weight of 1370 gms. The 2nd fetus had poor definition of fetal parts and no cardiac activity. Femur length was 46.6 cm corresponding to 25 weeks + 4 day. There was severe oligohydramnios. Placenta was normal in position. She underwent spontaneous preterm twin vaginal delivery.

The 1st twin was a preterm male baby of 1.4 Kg with poor Apgar score and was shifted to neonatal intensive care unit (NICU) for observation. His monozygotic twin was an intrauterine demise (IUD) baby. Immediate postnatal examination revealed a macerated and anomalous baby of 880 gm. Placenta and membranes were delivered in-toto. The IUD baby was sent for autopsy examination.

The external anomalies noted were a single inferior limb, imperforate anus, absence of external genitalia and urinary meatus, distended abdomen and single umbilical artery [Figure 1a & b]. The baby also had features of Potter's facies and anomaly of the left arm. Post-mortem radiographic images revealed multiple skeletal anomalies like sacral agenesis, vertebral dysgenesis at L4 - L5 level and single femur, thus classifying our patient as Type VII of Stocker and Heifetz classification of sirenomelia sequence which is the most severe form [Figure 2]. Abdominal ultrasonography was not performed. Internal anomalies included a blind bowel with absence of rectum, right renal agenesis with left hydronephrosis, tubular bladder, absent gonads and single umbilical artery [Figure 3]. Other internal organs were normal.




Single femur with absence of tibia and fibula and sacral agenesis.


Case 2

A 21-year-old unbooked primigravida at 38 week + 6 days of gestational age presented with spontaneous labour pains. Her routine blood investigations and serum viral markers were normal. Her blood group was A negative. Ultrasound scan on admission showed a single live intrauterine fetus of 27 weeks + 2 days of age with breech presentation, poor biophysical profile, inadequately sustained fetal cardiac activity, overlap of fetal parts and non-visualisation of femur. She delivered a stillborn and anomalous baby by normal vaginal route. At fetal autopsy, external examination revealed Potter’s facies, distended abdomen, undetermined sex, imperforate anus, absent urinary meatus and fused lower limbs [Figure 4A]. Radiographic images showed 2 femur, 2 tibia and 2 fibulae thereby classifying this case as Type I of Stocker and Heifetz classification of sirenomelia sequence [Figure 5]. Internal examination revealed atrial and ventral septal defects (ASD; VSD) [Figure 4B], absent thymus, kidney & adrenals and bilateral congenital cystic adenomatoid malformation type III.