First-Trimester Ultrasound: A Comparative Review of Guidelines

First-trimester sonographic examination remains a fundamental part of antenatal care, providing crucial information for the well-being of both the mother and fetus and leading to the best possible perinatal outcomes. This study aimed to review and compare the most recently published guidelines on first-trimester ultrasound. Therefore, a descriptive review of guidelines from the American Institute of Ultrasound in Medicine (AIUM), the Australasian Society of Ultrasound in Medicine (ASUM), the Association of the Scientific Medical Societies in Germany (AWMF), the International Society of Ultrasound in Obstetrics and Gynecology (ISUOG), the Society of Obstetrician and Gynecologists of Canada (SOGC) and the World Association of Perinatal Medicine (WAPM) regarding first-trimester scans was conducted. There is a consensus regarding the main parameters that should be evaluated, the qualifications of the examiner and specifications of the ultrasound machine, as well as the importance of informed consent. Additionally, the importance of careful visualization of fetal anatomy is discussed, with minor discrepancies regarding the appropriate protocol used. The use of combined first-trimester examination is encouraged by all the reviewed medical societies, although cell-free DNA testing is addressed only by a few, with similar indications. Controversy exists regarding the indications and appropriate gestational age at which the first-trimester scan should be performed, as well as the proper establishment of pregnancy dating. Notably, recommendations regarding fetal growth restriction (FGR) and diagnostic invasive procedures are made only by few medical societies, with the AWMF and SOGC addressing screening for FGR. Furthermore, invasive diagnostic testing is discussed by the AIUM, AWMF and SOGC, with differentiations among them regarding the indications for pursuing such procedures. First-trimester sonographic examination is essential for assessing fetal viability, establishing accurate pregnancy dating, evaluating fetal and maternal anatomy and calculating the risk of various fetal and maternal conditions. The implementation of evidence-based, unified protocols would advance both maternal and fetal outcomes.