Prenatal sirenomelia diagnosis in the first trimester: A case report and literature review.

Key Clinical Message: Sirenomelia is a lethal condition in the perinatal period. The sonographic examination in the first trimester can effectively detect sirenomelia with a high degree of accuracy. Furthermore, vascular examinations using color flow imaging and augmented imaging techniques such as 3D sonography can improve diagnostic accuracy. Parents should get advice from a multidisciplinary team concerning sirenomelia care and prognosis as soon as possible. Abstract: Sirenomelia is a rare condition with an uncommon congenital malformation; its most remarkable feature is lower extremity fusion with multiple visceral anomalies. Accordingly, the appearance resembles a mermaid's tail, hence mermaid syndrome. Sirenomelia has an incidence rate of 1.5-4.2 per 100,000 births, a male-to-female 2.7:1 ratio, and shows no differences across races. The condition is generally associated with renal agenesis, exterior genitalia defects, a single umbilical artery, and an imperforate anus. Here, we describe the first sirenomelia case in our hospital; a 13-week-old fetus with conjoined lower limbs was identified by ultrasound in the first trimester. We discuss this rare case with reference to the literature and provide insights on diagnosing this condition by ultrasound.