PhD defence: Simon Horsholt Thomsen
Mosaicism in the placenta: How did it happen? Can the result be trusted? What is the fetal prognosis?
Info about event
Time
Location
Auditorium C114-103+104, entrance C, Aarhus University Hospital
On Friday 18 September 2026 at 14:00, Simon Horsholt Thomsen defends his PhD dissertation entitled "Mosaicism in the placenta: How did it happen? Can the result be trusted? What is the fetal prognosis?".
Placental mosaicism - the presence of multiple different cell lines in the same placenta - is one of the most challenging findings in prenatal diagnosis. It creates considerable uncertainty and raises many important questions: Is the fetus affected? What is the risk of pregnancy complications? Can the result be trusted? And how should we counsel expectant parents?
Placental mosaicism is identified in 2-4% of all chorionic villus samples. In some cases, the chromosomal abnormality is also present in the fetus, whereas in others it is confined to the placenta. Even when the fetus is unaffected, there may still be an increased risk of complications such as fetal growth restriction. Furthermore, the chromosomal constitution of the placenta and fetus may prove to be more complex than initially anticipated.
Through Danish registry data and clinical studies, this PhD project investigates the implications of different types of placental mosaicism for fetal prognosis and pregnancy outcome. The results demonstrate that the associated risks vary considerably between different chromosomal abnormalities, and that structural chromosomal rearrangements require a more nuanced interpretation than previously recognized.
By providing new insights into the biological and clinical significance of placental mosaicism, this project contributes to improved counselling, supports clinical decision-making and a more individualized management of pregnancies affected by placental mosaicism.
The summary is written by the PhD student.
The defence is public and takes place in Auditorium C114-103+104, entrance C, Aarhus University Hospital. Please see the press release for more information.
Contact
PhD student Simon Horsholt Thomsen
Mail: sihoth@clin.au.dk
Phone: +45 28359927