Sirenomelia: A Detailed Fetal Autopsy Study

Abstract

Sirenomelia also known as mermaid syndrome, characterized by fused lower limbs, is a lethal and rare congenital abnormality. This is an extreme example of caudal regression syndrome caused by vascular steal of single umbilical artery. Sirenomelia is found approximately one in 100,000 live births and is usually fatal because of complications associated with pulmonary hypoplasia, abnormal development of the kidneys and urinary bladder. Most of the cases are associated with maternal diabetes and single umbilical artery.We report a case of sirenomelia terminated at 21weeks of gestation due to multiple congenital abnormalities. Antenatal scan of a25-year old primi revealed a single live fetus of 21 weeks gestation with severe olighydramnios, non-visualization of kidneys and bladder and lower part of the spine. This pregnancy was terminated and the specimen sent to the department of anatomy for fetal autopsy. On external examination,a tail like rudimentary single midline lower limb without foot was noted. There were no external genitalia and anal orifice. Internal examination revealed hypoplastic lungs, atrial septal and ventricular septal defects, aberrant right subclavian artery, hypoplastic abdominal aorta distal to the single umbilical artery, complete agenesis of urinary system, rectal agenesis and rudimentary indeterminate gonads.We would like to discuss the clinical features, etio-pathogenesis and review of literature of sirenomelia. Early diagnosis and termination of this lethal congenital anomaly results in minimizing the trauma related to the termination of pregnancy at advanced gestation.