OBJECTIVE: Evaluate the feasibility and quality of a national standardised mid-trimester ultrasound protocol using a consensus-based quality assessment (QA) scoring system. DESIGN: Multicenter prospective observational 'FLASH' study. SETTING: (i) Assessing the feasibility of a standardised protocol of 24 views at the mid-trimester scan, with 21 recommended and 3 additional views, in routine practice. (ii) Assessing the quality of these images by evaluating the presence of conformity criteria. (iii) Analysing the reliability between self-assessment and peer-assessment of the images. POPULATION: A total of 440 mid-trimester scans. METHODS: A consensus-based QA scoring system comprising 73 conformity criteria was established with 28 experts using a 3-round Delphi method. Secondly, we asked operators to record 5 consecutive routine mid-trimester scans. Images were analysed by the sonographer themselves and by a qualified expert according to the scoring system. The frequency of recorded images was calculated for each of the views. Factors associated with missing images per scan were evaluated. The robustness of conformity criteria was assessed by reliability between self-evaluation and peer-evaluation. MAIN OUTCOME MEASURES: Based on 9849 images, we observed feasibility of the 21 recommended standardised views for mid-trimester scan ranging from 88.5% to 100%. RESULTS: Most conformity criteria (64/73, 88%) were met in over 90% of cases. Gwet's AC1 correlation between expert evaluation (peer-evaluation) and participant evaluation (self-evaluation) was greater than 0.80 for 70/73 (96%) criteria. CONCLUSION: This large-scale 2-month 'flash' observational study demonstrates the feasibility and quality of a national standardised mid-trimester ultrasound protocol using a consensus-based QA scoring system.