Objective: To prove the utility of abnormal cardiac axis on the sonographic screening of congenital heart defects at 11+0 to 13+6 weeks of pregnancy in Korean population. Methods: This study was undertaken in Chung-Ang University hospital with expertise in fetal imaging in early gestation. Fetal cardiac axis was retrospectively evaluated between 11 0/7 and 13 6/7 weeks of gestation in 159 fetuses with evident four-chamber view. Cardiac axis was measured on the four-chamber view as the angle between the line that traces the long axis of the heart and the line that bisects the thorax in an anteroposterior direction. Confirmation of congenital heart disease was only based on the postnatal imaging. A normal fetal cardiac axis was characterized by a 90% confidence interval of the cardiac axis in fetuses without congenital heart defects. Multivariable logistic regression was used to assess the efficacy of the fetal cardiac axis. Results: Among 159 registered fetuses, 29 fetuses had an abnormal cardiac axis. A normal fetal cardiac axis was defined as 27 to 67°. On multivariable analysis for congenital heart defects, abnormal fetal cardiac axis (odd ratio [OR]=2.97; 95% confidence interval [CI]=1.11-7.94; p=0.030) and increased nuchal translucency (odd ratio [OR]=4.68; 95% confidence interval [CI]=1.82-12.04; p=0.001) were associated with increased likelihood of congenital heart defects compared to normal findings. Conclusion: The fetal cardiac axis could be a helpful tool for prenatal screening of congenital heart defects in the first-trimester.