Sirenomelia, often referred to as "mermaid syndrome," is a rare congenital condition where a baby is born with fused legs, giving the appearance of a mermaid's tail. This fascinating yet serious anomaly raises questions about the existence of mermaids and sheds light on the complexities of human development. It is a severe congenital malformation characterized by the fusion of the lower limbs. This condition results in the appearance of a single limb resembling a mermaid's tail, hence the nickname "mermaid syndrome."

In individuals with sirenomelia, the lower limbs are fused together, and there are often additional anomalies in the lower spine, gastrointestinal tract, and urogenital system. The severity of these malformations can vary, but they significantly impact the quality of life and require complex medical management.

Sirenomelia occurs in about 1 in 100,000 live births, making it one of the rarest congenital anomalies. The ratio can vary slightly depending on geographic and demographic factors. And although sirenomelia is extremely rare, it affects both males and females, but there is a slightly higher prevalence in males.

It is believed to result from abnormal vascular development during early embryonic growth. One theory suggests that an abnormality in the vitelline artery causes a disruption in blood supply to the lower limbs, leading to their fusion. Genetic and environmental factors may also play a role. This abnormality can often be detected during prenatal ultrasounds. Signs that may indicate sirenomelia include abnormal limb positioning, absence of kidneys, or a single lower limb. Early detection allows for better planning and management of the condition.