Mermaid is a tangible female creature that has a body like a human from head to waist, while the body parts from the waist, lower legs to feet resemble fish. This creature is often found in fiction and animated films. Do mermaids exist in the real world?

Sirenomelia Mermaid syndrome
Mermaid Syndrome (Sirenomelia)

What is Sirenomelia?

Sirenomelia comes from the word SIREN, a legendary creature in Greek mythology in the form of a woman with bird legs, with or without wings, playing a musical instrument, especially Harp. However, many people assume that mermaid and siren are the same, so mermaid is also considered as the siren.

Therefore, Sirenomelia is also called as Mermaid Syndrome, which is defined as congenital malformation or birth defect characterized by complete or partial fusion of the two lower limbs to the feet are shaped like mermaid tails or sirens.


This syndrome is rare, occurring in one in 100,000 pregnancies. Mermaid syndrome affects males more often than females by a ratio of 2.7-1.  Sirenomelia occurs with higher frequency in one twin of identical (monozygotic) twins than it does in fraternal (dizygotic) twins or individuals.

Baby born with Sirenomelia

Clinical manifestations

Not only the lower limbs abnormality that resembles mermaid tails, but other abnormalities can also occur in mermaid syndrome, including genitourinary and gastrointestinal abnormalities, lumbosacral spine and pelvic anomalies, also kidney agenesis.

The following signs and symptoms that can appear in mermaid syndrome:
  1. May have only one femur or two femurs within one shaft of the skin
  2. May have one foot, no feet or both feet, which may be rotated externally.
  3. The partial or complete absence of tailbone. Even, in some patients, abnormal front-to-back curvature of the spine (lordosis) may occur
  4. Imperforate anus or anorectal malformation. The condition in which a thin covering blocks the anal opening or the passage that generally connects the anus and rectum fails to develop.
  5. Urogenital abnormalities, including renal agenesis (absence of one or both kidneys), cystic malformation of the kidneys, absent urine vesica, urethral atresia.
  6. Absence of the gallbladder and/or the spleen.
  7. Omphalocele. The protrusion of a portion of the intestines through a hole near the belly button.
  8. Meningomyelocele or open spina bifida. The birth defect in which the spinal canal and the backbone do not close before the infant is born. In some cases, the spinal cord itself protrudes through a defect in the spinal column.
  9. Congenital heart defects 
  10. Pulmonary hypoplasia (severe underdevelopment of the lungs).

What are the factors that cause mermaid syndrome?

The exact cause of this syndrome is still unknown. However, researchers believe that environmental and genetic factors have a role in the development of the disorder. Most cases occur randomly for no apparent reason indicating environmental factors or new mutations in genes.

Most likely, Sirenomelia is multifactorial, which means several different factors can play an important role. Also, various genetic factors can cause abnormalities in different people (genetic heterogeneity). Researchers believe that genetic factors have teratogenic effects on the developing fetus. Teratogens are substances that can interfere with embryonic or fetal development.

Several studies have suggested vascular impairment or embryo damage during fusion at 28-32 days of gestation. Another theory is the presence of maternal risk factors for diabetes, smoking, exposure to high doses of retinoic acid, and exposure to heavy metals. Examinations Adequate pre-natal with ultrasonography can detect malformations earlier, preparing options for the patient's family for early termination.


Sirenomelia treatment is surgery. therefore, the treatment requires the coordinated efforts of a team of specialists. Surgeons, pediatricians, cardiologists, orthopedist surgeons, nephrologists, and other health care professionals may need to comprehensively and systematically.