RT Book, Section A1 Bianchi, Diana W. A1 Crombleholme, Timothy M. A1 D'Alton, Mary E. A1 Malone, Fergal D. SR Print(0) ID 1106401982 T1 Triploidy T2 Fetology: Diagnosis and Management of the Fetal Patient, 2e YR 2015 FD 2015 PB McGraw-Hill Education PP New York, NY SN 978-0-07-144201-5 LK obgyn.mhmedical.com/content.aspx?aid=1106401982 RD 2024/12/11 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.