Pregnancy care has gradually evolved over the last two decades, with a trend towards earlier detection and diagnosis of both maternal and fetal pathologies. At the core of this process, antenatal ultrasound allows to identify a large number of congenital malformations as early as the end of the first trimester. It has also become an increasingly specialized procedure, requiring considerable material and human resources. In this article, we review the basic principles of first-trimester ultrasound, focusing on most recent screening recommendations.