Low-level mosaic trisomy 13 at amniocentesis associated with a favorable outcome in a pregnancy

Objective: We present low-level mosaic trisomy 13 at amniocentesis associated with a favorable outcome in a pregnancy. Case report: A 39-year-old woman underwent amniocentesis at 17 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 47,XY,+13[8]/46,XY[20]. The woman underwent cord blood sampling at 22 weeks of gestation. Cytogenetic analysis of cord blood revealed a karyotype of 47,XY,+13[2]/46,XY[98]. Array comparative genomic hybridization (aCGH) analysis on the DNA extracted from cord blood revealed 10% gene dosage increase in chromosome 13. Prenatal ultra-sound findings were unremarkable. After genetic counseling, the parents decided to continue the pregnancy, and a 2,280-g healthy male baby was delivered at 38 weeks of gestation. The parental karyotypes were normal. The cord blood at birth had a karyotype of 47,XY,+13[1]/46,XY[49]. At age one month, interphase fluorescence in situ hybridization (FISH) analysis revealed no trisomy 13 signals in 100/100 buccal mucosal cells, and trisomy 13 signals in 2/54 (3.7%) urinary cells compared with 0/60 cells in the normal control. The neonate was doing well and presented neither phenotypic abnormalities nor psychomotor disorders at age two months. Conclusion: Low-level true mosaic trisomy 13 at amniocentesis without ultrasound abnormalities can be associated with a favorable outcome.(c) 2020 Taiwan Association of Obstetrics & Gynecology. Publishing services by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).