Originally published 2018-01-05.
Two photos of the baby girl born with sirenomelia in Kolkata in December 2017. She lived for about four hours after birth.
Sirenomelia is a very rare birth defect in which a baby's legs are fused together, along with serious problems in the lower spine, kidneys, bladder and genitals. It affects roughly one in 100,000 births and is usually fatal within hours or days. Its nickname, "mermaid syndrome", comes from the shape of the fused limbs, but for the families involved it is a medical emergency, not a fairy tale.
In December 2017 the condition made headlines worldwide after a baby girl was born with it at a government hospital in Kolkata, India, and died about four hours later. Her story, and the family's poverty, raised questions about why the condition happens, how it is found before birth and whether anyone survives it. The photos in this article are medical and may be upsetting, so they are blurred until you choose to view them.
The Kolkata case in December 2017
The mother, 23-year-old Muskura Bibi, gave birth naturally at Chittaranjan Deva Sadan Hospital, a state-run hospital in Kolkata, West Bengal. Indian medical news site Medical Dialogues reported the case on 10 December 2017. The baby's upper body had formed normally, but below the waist the legs were joined into a single limb and the lower body had not developed fully. She lived for about four hours.
The parents were labourers on very low wages. According to the hospital's child specialist, Dr. Sudip Saha, the family had not been able to pay for proper antenatal care or an ultrasound scan, so they only learned about the condition after the birth. "I had never seen such a baby before," he told reporters.
The newborn in the Kolkata hospital shortly after birth, with the fused lower limb typical of sirenomelia. Medical staff are supporting the baby, who has a clamped umbilical cord and an intravenous line in one hand. Photo shared on X (Twitter) by @bmicalculatoruk.
What sirenomelia is
Sirenomelia, also called sirenomelia sequence, is a congenital condition that forms in the first weeks of pregnancy. Besides the joined legs, babies usually have missing or underdeveloped kidneys, an absent or malformed bladder, missing external genitals and an imperforate anus, along with abnormalities of the lower spine and sacrum.
The kidney problems are the main reason most babies do not survive. Without working kidneys, a fetus produces little or no urine, which normally makes up much of the amniotic fluid in later pregnancy. Too little fluid (oligohydramnios) stops the lungs from developing properly, so many babies cannot breathe after birth.
Published studies put the birth prevalence at about one in 70,000 to one in 100,000. Many affected pregnancies end in miscarriage, a third to a half of babies are stillborn, and nearly all of the rest die in the newborn period.
Another view of the baby, lying on a hospital sheet. The upper body looks typical for a newborn, while the legs are fused from the hips down to a single foot-like end. Photo shared on X (Twitter) by @bmicalculatoruk.
What causes it
The exact cause is still debated. The leading idea, first proposed in 1927, is the "vascular steal" hypothesis. In many affected babies there is a single umbilical artery instead of the usual two, and an abnormal vessel takes blood from high up in the aorta to the placenta. The lower part of the body is then starved of blood and nutrients while it is forming, so the limbs and organs there do not develop properly.
Other researchers think the main problem is earlier damage to the tissue that forms the lower body, around the fourth week of pregnancy, possibly triggered by genetic or environmental factors. Doctors in Kolkata suggested poor maternal nutrition and reduced blood flow to the baby might have played a part, but in any single case the cause usually cannot be identified. Most cases occur without any family history.
Two associations stand out in the research:
- Identical twins: sirenomelia is roughly 100 to 150 times more common in identical twins than in single births or fraternal twins, which supports theories involving blood flow between twins and the placenta.
- Maternal diabetes: diabetes in the mother has been linked to sirenomelia and related lower-body defects, although not every study agrees.
None of this means parents caused the condition. It is not passed down in families in any predictable way, and a family that has had one affected pregnancy is not known to face a high risk of another. Anyone with questions about their own pregnancy should talk to a doctor.
A preserved specimen of a baby with sirenomelia in a medical museum, showing the single fused lower limb. Museum collections like this were long used to teach doctors to recognise rare birth defects. Image via Wikimedia Commons.
How it is diagnosed before birth
Sirenomelia can be detected on a prenatal ultrasound, sometimes as early as 14 weeks of pregnancy and more often in the second trimester. Sonographers may see a single lower limb, absent kidneys, an empty bladder area and a single umbilical artery. Very low amniotic fluid can make the picture harder to read, so specialist scans are sometimes needed.
Early diagnosis does not change the condition itself, but it gives families time to understand what is happening, plan delivery and decide on care with medical teams. In the Kolkata case, the family could not afford a scan, so the news came only in the delivery room. That gap is one of the starkest parts of the story, and it reflects how unequal access to routine antenatal care remains in many places.
Has anyone survived sirenomelia?
Early reports of the Kolkata case quoted claims that nobody had ever survived the condition. That is not correct. A small number of children whose kidneys worked at least partly have lived for years after complex treatment:
- Tiffany Yorks (United States, 1988–2016) had surgery to separate her legs before her first birthday and lived to 27, the longest-surviving patient reported.
- Milagros Cerrón (Peru, 2004–2019) had leg separation operations in 2005 and 2006 and lived to 15.
- Shiloh Pepin (United States, 1999–2009) never had her legs separated, received kidney transplants and lived to ten.
These children faced repeated surgery and lifelong medical problems, and they are rare exceptions. For most babies with sirenomelia, the absence of working kidneys means survival is not possible.
A second preserved specimen of a fetus with sirenomelia, displayed in a jar in a medical collection. The fused limb narrows to a single end, the feature that gave the condition its "mermaid" nickname. Image via Wikimedia Commons.
Was it really India's second case?
Local doctors described the Kolkata baby as the first case in West Bengal and the second in India, after a baby born in Uttar Pradesh in 2016 who lived for about ten minutes. That claim should be read with care. Sirenomelia has appeared in Indian medical journals for decades, so these were more likely the first cases to reach the news than the only ones ever seen. Because many births in rural areas happen without scans or specialist review, the true number is unknown.
What is clear is the human side of the story: a young couple with little money, no chance of preparing for a devastating diagnosis and only a few hours with their daughter. The best responses to cases like this are better access to antenatal care, compassionate support for grieving families and language that treats affected babies as children, not curiosities.
Sources: Medical Dialogues, 10 December 2017: India's second mermaid baby born in Kolkata but dies four hours later; Wikipedia: Sirenomelia. Hospital photos shared on X (Twitter) by @bmicalculatoruk; museum specimen photos via Wikimedia Commons.
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