Seeing the unseen The importance of prenatal screening

Through prenatal screening, we aim to reveal, discover and comprehend the unseen aspects of the fetus. It offers opportunities, reduces risks, and evaluates fetal health. Over the past decade, the field of prenatal screening has made tremendous progress. Whereas previously it was limited to a selected group, screening for chromosomal abnormalities is now offered to all pregnant individuals. While first trimester combined testing (FCT) was used before, nowadays the more accurate method involves analyzing cell free DNA (cfDNA) in maternal blood, using non-invasive prenatal testing (NIPT). For the detection of structural anomalies, ultrasounds are offered in the first- and second trimester of pregnancy.
This thesis studied the importance of the prenatal screening field during its developments and throughout pregnancy with emphasis on subtle markers, such as nuchal translucency and chromosomal anomalies, and the prenatal detection of structural anomalies during the first- and second trimester of pregnancy. Topics studied included adverse pregnancy outcome and early increased nuchal translucency, sonographic features of triploid pregnancies and their parental origin, the risk of gestational trophoblastic neoplasia in partial molar pregnancies, the consequences of eliminating FCT for early detection of fetal anomalies, the influence of an additional first trimester scan on the detection of congenital heart defects and the prevalence of their genetic origin.
This thesis concludes that identifying a fetal anomaly early in pregnancy provides parents with the opportunity to contemplate genetic testing and make autonomous reproductive choices, which include the option of terminating the pregnancy. However, prenatal screening, along with prenatal diagnostics, introduces uncertainty in some situations. It is essential to discuss not only the importance, but also the challenges of prenatal screening with future parents, ensuring they have realistic expectations. Because sometimes, the unseen remains unseen.