Abstract
In the last few years, the introduction of cell-free DNA has rapidly altered prenatal screening regimens and is increasingly offered as the second- or, at times, even the first-tier screening test. Should an early anomaly scan also be part of an up-to-date screening policy? This paper reappraises the value of fetal first-trimester ultrasonography. The primary aims of the first-trimester scan are to establish gestational age based on the measurement of fetal crown-rump length, to detect multiple pregnancy and chorionicity, and to measure fetal nuchal translucency thickness as part of a combined screening test for chromosomal abnormalities. With recent advancements in ultrasound technology, there is compelling evidence that a majority of fetuses with major structural abnormalities and almost half of them without chromosomal abnormalities can be detected in the first trimester. We focused on the first-trimester screening of fetal major defects, especially including fetal congenital heart disease and cleft lip and palate by ultrasound markers and views. Moreover, it is critical to highlight that after a detailed anomaly scan in the first trimester without major structural anomalies and positive genetic tests, the residual chance of favorable outcome in fetuses with isolated increased nuchal translucency is relatively high. The discussion on the role of cell-free DNA in prenatal screening is still ongoing. Even in the event of it becoming a first-line screening test for aneuploidies, the importance of a first-trimester fetal scan, including assessment of markers for other anomalies, remains undisputed.