What is Mermaid Syndrome?

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  • Last Modified Date: 04 October 2019
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Mermaid syndrome is also called sirenomelia and it is an extremely rare set of birth defects, which can vary in expression. The condition gets its name from one of the defects present, which is a fusing of the legs. The unseparated nature of the legs has been compared to a mermaid in appearance, hence the name.

If mermaid syndrome only had leg fusion, it might not be so very serious, but instead, children born with this congenital disorder have a wide variety of problems with other parts of the body. Genitals may be misshapen or absent, the bladder can be missing, spinal abnormalities may be present, and the kidneys may be seriously affected. Not that many years ago, the condition would have been considered always fatal within a few hours to days after a child is born, but there have been some successful surgeries that may ultimately alter outlook on treatment for this disease.

Several now “famous” patients have undergone treatments since the early 2000s. Shiloh Pepin, born in 1999, has received kidney transplants, restructuring of her urinary tract and other interventions. Milagros Cerron, born in 2004, had a successful surgery to separate her legs, and she is able to walk. Both girls face a lifetime of medical care. Shiloh received her second kidney transplant in 2007, but the fact that both girls did not die at birth or before it, is encouraging.


The defects associated with mermaid syndrome occur about once in 100,000 births. However, with a birth rate of over four million children a year in the United States, that would suggest about 40 children a year are born with this condition, in the US alone. These statistics must be sobering, if there are only a handful of children who have thus far managed to survive. Part of the issue may be medical prejudice toward not treating kids with mermaid syndrome, and strong recommendations from doctors that they be allowed to die, but proven treatment might alter this mindset in time.

Another reason survival can be so poor in mermaid syndrome is that severity of birth defects and types of defects may vary. With less severe forms, it’s possible that children will be able to survive to treatment. Greatly severe defects may mean the condition simply isn’t survivable for some of the children born with it. Some children do not even live to birth, and so part of assessing and treating mermaid syndrome in the future may be determining the types and severity of defects that exist.


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Post 5

I am a mother who had a newborn at 38 weeks along, who was born with this disease. It lived 15 minutes. The year was 1980. I was a healthy 18 year old female with no medical conditions.

I read the message about the doctor's sister, which makes me wonder if I may have been exposed to toxins. I worked in a nursing home as a house keeper at the time. So I was exposed to a lot of chemicals.

I should also add my husband is a Vietnam vet and he was exposed to Agent Orange. I am wondering if this might have been a factor. This child would have been his first born, but not my first born.

I am doing a report on the subject for a course at college. It still seems there is little known about this disease. With the technology we have today, there should be more medical information about it.

My baby's upper half was pretty much normal looking, but I never saw the deformities. I was told its legs appear fused. We buried the baby a few days later, and the funeral director told us that it was missing a lot of internal organs.

Post 4

I am a mother who had a baby who passed away for mermaid syndrome. The reason she formed the way she did is I had identical twins so when they split they didn't split right. I found out I was pregnant at 2 weeks and never drank. I took every prenatal precaution. She lived for two hours after birth. I carried her for 36 weeks, and she lived for her identical sister who is almost 1.

Post 3

I saw mermaid syndrome patient Shiloh Pepin on TV before she passed away in 2009. She was such a strong and positive girl! She was ten at the time and I believe she's the longest-living person who had mermaid syndrome.

I think she was such a great example and inspiration to others with the syndrome, as well as parents and doctors. She proved that anything is possible.

When she was born, doctors had expected her to live for only several days at the most. But she proved them wrong and lived for a whole ten years. The most amazing part was how positive and happy she was during her TV interview! She certainly didn't let the condition bring her down!

Post 2

@burcidi-- Wow! I had no idea that the first weeks of pregnancy was so important in terms of developing birth defects.

Do you think that mermaid syndrome can be prevented if mothers take extra caution during this time and stay away from all the possible culprits even before they become pregnant?

And I'm sure that it's possible to diagnose the syndrome pretty early on in the pregnancy with the use of a fetal ultrasound, right? So the pregnancy could be terminated early since the rate of survival for people with mermaid syndrome seems low. I'm sure that this would be a very difficult and painful decision to take for any mother though.

This article has definitely opened my eyes up about the possible complications during pregnancy and what the results may be. I have diabetes so this will be something I will need to consider and be careful about before getting pregnant.

Post 1

My brother is a doctor and he came over for dinner to my house last week. He was talking about an infant that was born with the mermaid syndrome and passed away ten minutes after birth.

I had never heard about this fetal syndrome before so he told me a little about the causes. I don't remember all the technical words he used. But from what I understand, the syndrome is caused by an injury to the embryo during the 3rd week of pregnancy.

This is apparently the time when the embryo starts forming the skeleton, reproductive organs and other tissues. He said that the injury could be caused by lots of different things like the mother having

an infection, taking medications or being exposed to toxins, using alcohol and tobacco and chronic diseases like diabetes and hypothyroid.

He also showed me a picture of a newborn with the syndrome on the net and it was quite unbelievable. The infant had a single leg and two misshaped feet at the end. A genital organ could not be seen at all and the skeleton was clearly formed abnormally. The part of the infant which looked closest to normal was the head but the neck looked much thicker than usual.

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