TY - CHAP M1 - Book, Section TI - Sirenomelia A1 - Bianchi, Diana W. A1 - Crombleholme, Timothy M. A1 - D'Alton, Mary E. A1 - Malone, Fergal D. PY - 2015 T2 - Fetology: Diagnosis and Management of the Fetal Patient, 2e AB - Key PointsIncidence is 1 in 60,000 livebirths.Results from localized injury or insult to caudal end of developing embryo between days 13 and 22.Classified into 7 types according to the number of long bones present in the lower extremity.Associated with monozygotic twinning.First trimester sonographic findings include fused lower limb and increased nuchal translucency.Second trimester sonographic findings include single umbilical artery, bilateral renal agenesis, oligohydramnios, and growth restriction.Differential diagnosis includes bilateral renal agenesis and caudal regression syndrome.Chromosomes are usually normal.Prognosis is extremely poor for extrauterine survival. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/03/28 UR - obgyn.mhmedical.com/content.aspx?aid=1106399789 ER -