Approach to Performing a Dating Scan (Ultrasound):

Abstract

The first-trimester dating scan is a cornerstone of obstetric ultrasound, providing the most accurate estimation of gestational age and early assessment of pregnancy viability. Performed ideally between 7 and 13+6 weeks of gestation, the scan involves a systematic approach: confirmation of intrauterine pregnancy, evaluation of the gestational sac and yolk sac, identification of the embryo or fetal pole, and documentation of cardiac activity. The crown-rump length (CRL) remains the gold standard for gestational dating in this period, with an accuracy of ±3–5 days. Additional findings include assessment of the number of fetuses, evaluation of uterine and adnexal structures, and early screening markers such as nuchal translucency when appropriate. Accurate dating reduces the risk of misclassification of growth restriction or post-term pregnancy and guides appropriate antenatal care.