TY - CHAP M1 - Book, Section TI - Triploidy 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 PointsOccurs in 1% to 2% of clinically recognized conceptions but only 1/10,000 livebirths. Not associated with advanced maternal age.Most cases are 69, XXY (60%) or 69, XXX (37%); only 3% of cases are 69,XYY.In the type I phenotype the fetus is relatively well grown with a large cystic placenta.In the type II phenotype the fetus is markedly growth restricted with a disproportionately large head and a small, noncystic placenta.One third of cases survive beyond 15 weeks and are associated with abnormal maternal serum screen results.The longest postnatal survival for an affected infant was 10frac12 months. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/03/29 UR - obgyn.mhmedical.com/content.aspx?aid=1106401982 ER -