**7. Efficiency of the fetal cardiac scan**

Although the most frequent congenital malformations, CHDs are among the most frequently missed [18, 55]. The efficiency of the cardiac scan is reported with great variation, depending on the scanning protocol, examiner experience, equipment quality and scanning conditions [18, 56–58]. It appears that the use of 4CV alone detects up to 77% of CHD, while adding OTV increases prenatal detection to 83–92% of major abnormalities.
