This document outlines the key aspects assessed in first, second, and third trimester ultrasound scans. The second trimester scan, done at 18-20 weeks, is most important for detecting anomalies. It involves a detailed assessment of the fetal head and neck, three scan planes of the brain, spine, heart, lungs, abdomen, extremities, face, and umbilical cord. The targeted anomaly scan looks for abnormalities in all major organ systems and rules out conditions like spina bifida and Down syndrome. Fetal growth and anatomy are also evaluated in the third trimester scan.