How Mermaid Syndrome Works


As is sometimes the case with genetic anomalies and mutations, sirenomelia or "mermaid syndrome" conjures certain fanciful images that have nothing to do with the traumatic effects associated with the actual medical anomaly.

Sirenomelia is so named because the birth defect involves the apparent fusing of the legs into a single lower limb, with the out-turned feet often resembling fish fins. The defect also commonly affects the kidneys, large intestines and genitalia. The condition sometimes affects the spine, brain and lungs as well.

According to Healthline.com, this rare condition occurs when a fetus develops only one umbilical artery (which pumps blood from the fetus to the placenta) and one umbilical vein (which returns blood to the fetus), while normal fetuses develop two umbilical arteries and one umbilical vein. The altered arrangement causes less blood and nutrition to reach the lower body, leading to the fused limbs and underdeveloped array of organs.

According to the Madisons Foundation, the condition affects roughly 1 in every 60,000 to 100,000 live births. Of the 300 reported cases, few survived more than several days -- and they required extensive medical care. As far as I can tell, the only living individuals with sirenomelia are Shiloh Pepin of the United States (you can visit her family's Web site here), Milagros Cerrón Arauco of Peru (here's a HowStuffWorks.com video on her case) and Tiffany Yorks of the United States.

It's hard not to be awed by these three survival stories. At the same time, does this rare condition receive more media attention due to its sensational aspects? I can't help but think of children born every day with conditions that don't make for as snappy a headline.

For more information on how you can help children with birth deflects and fight preventable defects around the world, visit the the March of Dimes.

Learn more at HowStuffWorks.com: How Childbirth Works How Pregnancy Works Should you save your baby's umbilical cord blood? HowStuffWorks.com's Birth & Infancy Channel


About the Author: Robert Lamb spent his childhood reading books and staring into the woods — first in Newfoundland, Canada and then in rural Tennessee. There was also a long stretch in which he was terrified of alien abduction. He earned a degree in creative writing. He taught high school and then attended journalism school. He wrote for the smallest of small-town newspapers before finally becoming a full-time science writer and podcaster. He’s currently a senior writer at HowStuffWorks and has co-hosted the science podcast Stuff to Blow Your Mind since its inception in 2010. In his spare time, he enjoys traveling with his wife Bonnie, discussing dinosaurs with his son Bastian and crafting the occasional work of fiction.