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Trisomy 8 mosaicism in the placenta: a Danish cohort study of 37 cases and a literature review
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  • Simon Horsholt Thomsen,
  • Ida Charlotte Bay Lund,
  • Christina Fagerberg,
  • Iben Bache,
  • Naja Becher,
  • Ida Vogel
Simon Horsholt Thomsen
Aarhus University Hospital
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Ida Charlotte Bay Lund
Aarhus University Hospital
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Christina Fagerberg
Odense University Hospital
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Iben Bache
University of Copenhagen
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Naja Becher
Aarhus University Hospital
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Ida Vogel
Aarhus University Hospital
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Abstract

Objective: To evaluate the risk of fetal involvement when trisomy 8 mosaicism (T8M) is detected in chorionic villus samples (CVS). Design: A retrospective descriptive study of registered cases in Denmark and a systematic literature review. Setting: Cases of T8M in CVS registered in Denmark between January 1983 and March 2019 and published literature until March 2019. Sample: A total of 37 registered pregnancies in Denmark and 60 published cases. Methods: Registered pregnancies with T8M in CVS were identified through a database search. Published cases of T8M were found through a systematic literature search and backward snowballing. Pregnancies with T8M in CVS and no additional numerical chromosomal aberrations were included. Main outcome measures: Fetal involvement defined as T8M in amniotic fluid (AF) or fetal tissue. Results: T8M detected in a CVS was associated with fetal involvement in 18 out of 97 pregnancies (18.6% [95%CI: 11.4-27.7]). Eight out of 70 (11.4% [95%CI: 5.1-21.3]) interpreted prenatally to be confined placental mosaicism (CPM) were found to be true fetal mosaicisms (TFM). Conclusion: T8M detected in CVS poses a significant risk of fetal involvement, and examination of AF and/or fetal tissue should be offered. However, a normal result of AF still has a considerable residual risk of fetal involvement. Genetic counselling at an early gestational age is essential, and follow-up ultrasonography should be performed to predict fetal involvement if possible. Funding: Ida Vogel is funded by a research grant from the Novo Nordic Foundation: NNF16OC0018772 Keyword: Trisomy, mosaicism, prenatal