Fetal ultrasound screening for preeclampsia is currently recommended between 20-23 weeks for low-risk pregnancies and between 12-14 weeks for high-risk pregnancies. When termination of pregnancy is an option, the earlier the diagnosis is made the better for the pregnant woman and minimizes suffering. However, the small size of the fetal heart in early pregnancy, the poor clarity of the ultrasound images, the diagnostic accuracy ring, and the fact that the fetal heart is a dynamic developmental process, some congenital heart diseases that are not apparent early but will progress over the course of pregnancy cannot be detected early. Therefore, early gestational echocardiography is only indicated for high-risk fetuses and often needs to be repeated up to 18-24 weeks of gestation to improve the rate and accuracy of fetal cardiac anomalies. At 18 to 24 weeks of gestation, the fetal heart development has gradually become perfect, and the intracardiac structures are clearly shown, and the fetal mobility and amniotic fluid volume are large, so the display rate of various sections can reach 100%. In late pregnancy, due to the decrease of amniotic fluid, large fetus, relatively fixed body position, and mostly occipital anterior position, the sound transmission window is poor, and the sound beam is easily affected by the fetal spine and rib shadow, which makes it difficult to display clear images, and the examination effect is poor.