Objective To evaluate our ability in classifying the fetal heart as normal or abnormal during the 1st trimester scan through fetal cardiac examination and determining the best time for this examination. Methods This was a prospective study performed on 3240 pregnant women to examine the fetal heart. Four chambers view and ventricular outflow tracts were mainly examined during the scan. We used grayscale and color mapping in the diagnosis. Color Doppler was used if additional information was needed, and all patients were rescanned during the 2nd trimester to confirm or negate our diagnosis. Results The cardiac findings were normal at both scans in 3108 pregnancies. The same cardiac abnormality was detected at both scans in 79 cases. In 36 cases there was false-positive diagnosis at the early scan; in 20 of these cases, there were mildly abnormal functional findings early in pregnancy with no abnormality found later. In 17 fetuses, there was discordance between the early and later diagnosis due to missed or incorrect diagnoses. The best time to do fetal heart examination during 1st trimester is between 13 and 13 + 6 weeks. Conclusion A high degree of accuracy in the identification of congenital heart disease (CHD) can be achieved by a 1st trimester fetal echocardiography.
Keywords: 1st trimester; congenital heart disease; fetal echocardiography; fetal heart; matching; mismatching.