Mosaic trisomy 18 at amniocentesis associated with a favorable fetal outcome in a pregnancy

Chih Ping Chen*, Te Yao Hsu, Ching Chang Tsai, Schu Rern Chern, Shin Wen Chen, Fang Tzu Wu, Peih Shan Wu, Chen Chi Lee, Li Feng Chen, Chen Wen Pan, Wayseen Wang

*Corresponding author for this work

Research output: Contribution to journalJournal Article peer-review

3 Scopus citations

Abstract

Objective: We present prenatal diagnosis of mosaic trisomy 18 by amniocentesis associated with a favorable fetal outcome in a pregnancy. Case report: A 42-year-old, gravida 4, para 2, woman underwent amniocentesis at 18 weeks of gestation because advanced maternal age. Amniocentesis revealed a karyotype of 47,XX,+18[6]/46,XX[17]. Simultaneous array comparative genomic hybridization (aCGH) on uncultured amniocytes showed the result of 45% mosaicism for trisomy 18. At 25 weeks of gestation, the woman underwent repeat amniocentesis which revealed a karyotype of 47,XX,+18[10]/46,XX[24]. Simultaneous aCGH on uncultured amniocytes showed the result of arr 18p11.32q23 (148,963–78,012,829) × 2.3 [GRCh (hg19)] with a log2 ratio of 0.2–0.25 compatible with 30–38% mosaicism for trisomy 18. The parental karyotypes were normal. Prenatal ultrasound was unremarkable. Interphase fluorescence in situ hybridization (FISH) on uncultured amniocytes showed 27% (27/100 cells) mosaicism for trisomy 18. Quantitative fluorescent polymerase chain reaction (QF-PCR) on uncultured amniocytes excluded uniparental disomy (UPD) 18. Non-invasive prenatal testing (NIPT) analysis at 34 weeks of gestation revealed a significant gene dosage increase of chromosome 18 (29.95; normal control: −3.0–3.0). At 39 weeks of gestation, a 2840-g phenotypically normal baby was delivered. The cord blood had a karyotype of 47,XX,+18[8]/46,XX[32]. The placenta was trisomy 18 of maternal origin. The umbilical cord had a karyotype of 47,XX,+18[2]/46,XX[38]. At age 1½ months, the peripheral blood had a karyotype of 47,XX,+18[5]/46,XX[35], and FISH analysis on buccal mucosal cells revealed 2% (2/102 cells) mosaicism for trisomy 18. When follow-up at age seven months, the neonate was phenotypically normal, and the peripheral blood had a karyotype of 47,XX,+18[1]/46,XX[39]. Conclusions: Mosaic trisomy 18 at amniocentesis without abnormal fetal ultrasound can be associated with a favorable outcome, and the abnormal trisomy 18 cell line may decrease progressively after birth.

Original languageEnglish
Pages (from-to)690-694
Number of pages5
JournalTaiwanese Journal of Obstetrics and Gynecology
Volume61
Issue number4
DOIs
StatePublished - 07 2022

Bibliographical note

Publisher Copyright:
© 2022

Keywords

  • Amniocentesis
  • Mosaic trisomy 18
  • Mosaicism
  • Prenatal diagnosis

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