Trisomy 8 mosaicism in the placenta: a Danish cohort study of 37 cases
and a literature review
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