Sirenomelia in the First Trimester

Abstract

This case report demonstrates an early detection of sirenomelia at 12 weeks' gestation. Sirenomelia, also known as “mermaid syndrome,” has been noted since the Greco-Roman period. As with the mermaid mythology, sirenomelia is characterized by a single lower extremity with varying appearances of severity of the lower extremity anatomy. Mermaid syndrome is not considered a genetic defect but is associated with monozygotic twinning and maternal diabetes. Sirenomelia is a rare disorder that is difficult to diagnosis by sonography due to oligiohydramnios usually associated with the disorder. This case represents a late first-trimester diagnosis of sirenomelia without oligiohydramnios.