Study population
The study population was randomly selected in the pregnant women presented to our center from July 2018 to December 2019. Fetuses with confirmed CHD or extracardiac abnormalities were excluded. Mothers with gestational anemia, diabetes, hypertension, and other high-risk factors were also excluded. All fetuses involved were singletons. In total, 123 pregnant women were enrolled in this study. Maternal gestation age ranged from 20 to 37 weeks. Informed consent was obtained from each patient and the study was approved by the Ethics Committee of Shengjing Hospital of China Medical University. All cases underwent a month postnatal echocardiography follow-up.