Cardiac screening examination of the fetus: guidelines for performing the ‘basic’ and ‘extended basic’ cardiac scan

Congenital heart disease (CHD) is a leading cause of infant mortality, with an estimated incidence of about 4–13 per 1000 live births1–3. Between 1950 and 1994, 42% of infant deaths reported to the World Health Organization were attributable to cardiac defects4. Structural cardiac anomalies were also among the most frequently missed abnormalities by prenatal ultrasonography5,6. Prenatal detection of CHD may improve the pregnancy outcome of fetuses with specific types of cardiac lesions7–11. Prenatal detection rates have varied widely for CHD12. Some of this variation can be attributed to examiner experience, maternal obesity, transducer frequency, abdominal scars, gestational age, amniotic fluid volume, and fetal position13,14. Continuous training of healthcare professionals based on feedback, a low threshold for echocardiography referrals and convenient access to fetal heart specialists are particularly important factors that can improve the effectiveness of a screening program3,15. As one example, the major cardiac anomaly detection rate doubled after implementing a two-year training program at a medical facility in Northern England16. The ‘basic’ and ‘extended basic’ cardiac ultrasound examinations are designed to maximize the detection of heart anomalies during a second-trimester scan17. These guidelines can be used for evaluating low-risk fetuses that are examined as a part of routine prenatal care18–20. This approach helps to identify fetuses at risk for genetic syndromes and provides useful information for patient counseling, obstetrical management and multidisciplinary care. Suspected heart anomalies will require more comprehensive evaluation using fetal echocardiography.