|Classification and external resources|
This condition is found in approximately one out of every 100,000 live births (about as rare as conjoined twins) and is usually fatal within a day or two of birth because of complications associated with abnormal kidney and urinary bladder development and function. More than half the cases of sirenomelia result in stillbirth and this condition is 100 times more likely to occur in identical twins than in single births or fraternal twins. It results from a failure of normal vascular supply from the lower aorta in utero. Maternal diabetes has been associated with caudal regression syndrome and sirenomelia, although a few sources question this association.
VACTERL-H is an expanded form of the VACTERL association that concludes that this diagnosis is a less severe form of sirenomelia. The disorder was formerly thought to be an extreme case of caudal regression syndrome; however, it was reclassified to be considered a separate condition.
Notable cases 
Only a handful of patients who did not have the usual kidney and bladder complications have survived beyond birth with this condition, 3 of them being:
Milagros Cerrón 
|Milagros Cerrón Arauco|
|Born||April 27, 2004 (age 9)
Milagros Cerrón Arauco was born on April 27, 2004, in Huancayo, Peru. Although most of Milagros’ internal organs, including her heart and lungs, are in perfect condition, she was born with serious internal defects, including a deformed left kidney and a very small right one located very low in her body. In addition, her digestive, urinary tracts and genitals share a single tube. This birth defect occurs during the gastrulation week (week 3) of embryological development. Gastrulation establishes the three germ layers: ectoderm, mesoderm and endoderm. It seems that complications such as defects in the urogenital system as mentioned above can be possibly due to malformations in the intermediate mesoderm.
A four-hour operation to insert silicone bags between her legs to stretch the skin was successfully completed on February 8, 2005. A successful operation to separate her legs to just above the knee took place May 31, 2005, in a "Solidarity Hospital" in the district of Surquillo in Lima. The procedure, however, was so intensive that she became traumatized to the degree of losing her ability to form proper speech patterns, leaving her nearly mute. It is not yet known if this is a physiological or psychological condition. However, at Milagros' second birthday, her mother reported that she knew more than 50 words. A second operation to complete the separation up to the groin took place on September 7, 2006. A few weeks later, she took her first steps.
Her doctor Luis Rubio said he was pleased with the progress Milagros had made, but cautioned that she still needed 10 to 15 years of rehabilitation and more operations before she could lead a normal life. Particularly, she will require reconstructive surgery to rebuild her rudimentary anus, urethra and genitalia.
Milagros' parents are from a poor village in Peru's Andes Mountains; the Solidarity Hospital has given a job to her father Ricardo Cerrón so that the family can remain in Lima, while the City of Lima has pledged to pay for many of the operations.
Tiffany Yorks 
|Born||May 7, 1988 (age 25)
Tiffany Yorks of the United States (born May 7, 1988) underwent successful surgery in order to separate her legs before she was one year old. She is the longest-surviving sirenomelia patient to date. She currently has enduring mobility issues due to her fragile leg bones. She compensates by using crutches or a wheelchair if she sustains a bad fracture.
Shiloh Pepin 
|Shiloh Jade Pepin|
|Born||August 4, 1999
Kennebunkport, Maine, United States
|Died||October 23, 2009 (aged 10)
Shiloh Jade Pepin (August 4, 1999 – October 23, 2009) was born in Kennebunkport, Maine, United States on August 4, 1999, with her lower extremities fused, no bladder, no uterus, no rectum, only 6 inches of large colon, no vagina, and with only one quarter of a kidney and one ovary. Her parents initially anticipated she could expect only a few months of life. Her natural kidney failed when she was just 3 months old. After that she was on dialysis. A kidney transplant at age 2 lasted a number of years, and in 2007 a second kidney transplant was successful. She attended Consolidated Elementary School. Shiloh was the only one of the three survivors of sirenomelia without surgery for separation of the conjoined legs. She died fighting a serious case of pneumonia on October 23, 2009, at Maine Medical Center in Portland, Maine, at the age of 10. Shiloh gained a following of admirers by documenting her condition on TV, Facebook and the Internet.
- Kallen, B; Castilla, E E; Lancaster, P A; Mutchinick, O; Knudsen, L B; Martinez-Frias, M L; Mastroiacovo, P; Robert, E (1992). "The cyclops and the mermaid: An epidemiological study of two types of rare malformation". Journal of Medical Genetics 29 (1): 30–5. doi:10.1136/jmg.29.1.30. PMC 1015818. PMID 1552541.
- Sammons, Mary Beth (November 26, 2009). "10-Year-Old Girl Born With Legs Fused Together". AOL. Archived from the original on November 26, 2009.
- Abraham M. Rudolph, Robert K. Kamei and Kim J. Overby (2002). Rudolph's Fundamentals of Pediatrics. McGraw Hill. p. 217. ISBN 978-0-8385-8450-7. Retrieved 2008-04-21.[verification needed]
- Assimakopoulos, E; Athanasiadis, A; Zafrakas, M; Dragoumis, K; Bontis, J (2004). "Caudal regression syndrome and sirenomelia in only one twin in two diabetic pregnancies". Clinical and experimental obstetrics & gynecology 31 (2): 151–3. PMID 15266776.
- Onyeije, Chukwuma; Sherer, David; Handwerker, Sara; Shah, Leena (2008). "Prenatal Diagnosis of Sirenomelia with Bilateral Hydrocephalus: Report of a Previously Undocumented form of VACTERL-H Association". American Journal of Perinatology 15 (3): 193–7. doi:10.1055/s-2007-993925. PMID 9572377.
- BBC News 24, September 7, 2006,"Mermaid" girl's legs separated
- Daily Mail September 27, 2006, "Mermaid" girl takes her first unaided steps
- BBC News September 28, 2006, "Mermaid" girl takes first steps
- "'Mermaid' girl takes first steps". BBC News. September 26, 2006. Retrieved May 23, 2010.
- "'Mermaid girl' to have legs split". BBC News. February 4, 2005. Retrieved May 23, 2010.
- TV program Body Shock, 10–11 pm, 18 May 2010, Channel 4
- Laura Dolce (2009-10-23). "Community saddened at 'Mermaid girl' Shiloh Pepin's passing". SeacoastOnline.com. Retrieved 2011-12-01.
- Taori KB, Mitra K, Ghonga NP, Gandhi RO, Mammen T, Sahu J (2002). "Sirenomelia sequence (mermaid): Report of three cases". Indian J Radiol Imaging 12 (3): 399–401.
- Birth Disorder Information Directory – contains many pointers to other references