Shiloh Pepin, of Kennebunk, Maine, was born with Sirenomelia, otherwise known as Mermaid Syndrome. Sirenomelia is incredibly rare, and usually results in death after a few days.
The Mermaid girl had fused legs, one kidney and one set of lower genitals as part of her condition. The name of her condition is officially called Sirenomelia. Life expectancy is significantly reduced.