TY - CHAP M1 - Book, Section TI - Trisomy 18 A1 - Bianchi, Diana W. A1 - Crombleholme, Timothy M. A1 - D'Alton, Mary E. A1 - Malone, Fergal D. Y1 - 2015 N1 - T2 - Fetology: Diagnosis and Management of the Fetal Patient, 2e AB - Key PointsSecond most common autosomal trisomy in liveborn infants.Eighty to 85% of cases result from full trisomy, 10% are mosaics, and 5% are due to translocation.Incidence is about 1 in 3000 livebirths. Females are more likely to be born alive and survive longer.Most affected fetuses have more than one sonographic abnormality. Most common sonographic abnormalities include IUGR, cardiac structural anomalies, choroid plexus cysts, central nervous system anomalies, and overlapping fingers/clenched hands.Associated with low maternal serum screening levels of pregnancy-associated plasma protein A, estriol, α-fetoprotein, and β human chorionic gonadotropin.Median postnatal survival for males is 1 to 2 months, and for females it is 9 to 10 months. The presence of a heart defect (surprisingly) does not affect postnatal survival time. About 5% to 10% of infants survive until their first birthday.All long-term survivors are profoundly retarded. Despite this, there are increasing reports in the literature of aggressive postnatal treatment, including mechanical ventilation, cardiovascular drugs, parenteral nutrition, and surgical repair of congenital anomalies.Reports exist of adults with mosaic trisomy 18 who have normal intelligence. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/04/16 UR - obgyn.mhmedical.com/content.aspx?aid=1106401884 ER -