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Two cases of placental T21 mosaicism: challenging the detection limits of non-invasive prenatal testing


  • Funding sources: Shanghai Committee of Science and Technology, China (Grant no.10DZ1951205).

  • Conflicts of interest: David Cram is an employee of Berry Genomics C., Limited.


What's already known about this topic?

  • Confined placental mosaicism (CPM) is a known biological phenomenon that can lead to false positive non-invasive prenatal test results.
  • The small number of false negative non-invasive prenatal test results reported to date are believed to be because of a low fetal DNA fraction in maternal plasma and/or placental mosaicism

What does this study add?

  • The degree and compartmentalization of placental mosaicism can potentially reduce the effective output of fetal DNA into the maternal circulation to steady state levels below the detection limit of non-invasive prenatal testing, leading to a false negative result