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Congenital heart disease (CHD) is a common form of congenital malformation associated with significant morbidity and mortality. Antenatal diagnosis of life-threatening forms of CHD may help to improve survival and morbidity as well as allowing parental choice and preparation. The diagnosis of CHD during fetal life can be made with a very high level of diagnostic accuracy in tertiary centres dealing with high-risk pregnancies. However, most cases of CHD will occur in low-risk groups and will only be detected by screening at the time of obstetric ultrasound scans. The concept of antenatal screening for CHD was introduced in the UK over 20 years ago, and current national guidelines recommend that the heart should be examined at the time of the obstetri