A novel, incidental finding of blood chimerism

Did you know maternal blood chimerism can be detected during cell-free DNA screening? Neither did we, until this happened.

There are many biological reasons for discordant cfDNA fetal sex results. Theoretically, blood chimerism has always been one of these reasons.

However, this is the first known case reported in the literature demonstrating maternal blood chimerism as the cause of discordant cfDNA fetal sex results.

What did we find?

  • Discordant cell-free DNA fetal results were caused by maternal blood chimerism.1
  • Mother’s medical history, karyotype and ABO typing were consistent with a diagnosis of blood chimerism.1
  • Maternal chimerism should be considered as a differential diagnosis for discordant cfDNA fetal sex results.1
  • Follow-up to uncover the reason for discordant cfDNA results often requires coordination between laboratory personnel and the clinical care team.


This research was presented at the 2019 American College of Medical Genetics (ACMG) Annual Meeting.

Download the poster

Have questions?

Dive deeper on how this research uniquely impacts your practice by contacting us. We’ll give you direct access to our researchers.

Email us


  1. Tschirgi et al. Cell-free DNA screening detects maternal blood chimerism – A case report. Poster presented at American College of Medical Genetics (ACMG) Annual Meeting 2019. Seattle, WA.