Prenatal cell-free DNA screening for rare chromosome abnormalities and adverse pregnancy outcomes

This thesis examines prenatal cell-free DNA screening for fetal chromosome anomalies, known as non-invasive prenatal testing (NIPT). We evaluate the accuracy of NIPT for rare chromosome anomalies, and find it significantly lower than for common conditions like trisomy 21. A major cause of false-positive results is confined placental mosaicism (CPM), where genetic anomalies affect the placenta. We assess the prevalence of CPM among false-positive NIPT results and examine for any associated pregnancy complications. Finally, we conduct surveys to understand the expectations, understanding, and preferences of pregnant individuals undergoing NIPT, emphasizing the need for informed counselling and awareness of test limitations.