During the fetal period, because the fetal heart is smaller and the heart rate is faster, the diagnosis of TAPVC by prenatal routine ultrasound is very difficult. Only when a more obvious total pulmonary vein is formed behind the left atrium, prenatal ultrasound is easier to find [3], so the general prenatal routine ultrasound is easy to miss diagnosis. Especially during the most important screening period, if the ultrasound image is not standard, it is easier to miss diagnosis. Conclusion and analysis of the causes TAPVC missed diagnosis may be as follows :1. During the fetus due to special hemodynamic effects, the left and right atrium and ventricle are basically symmetrical, there is no obvious right atrium enlargement, left atrium narrowing and other more obvious indirect cardiac changes. 2. there is space overlap between the left posterior pulmonary vein and the left atrium, it is easy to mistake for the presence of the pulmonary venous angle, while it is believed that the pulmonary venous blood flow drains to the left atrium, resulting in missed diagnosis of TAPVC. 3. the application of color doppler technique is not standard, usually, the color blood flow velocity scale is dropped to about 20 cm/s so that the pulmonary venous blood flow can be better observed. If the scale is too high, it is easy to block the low-speed pulmonary venous blood flow, and lead to missed diagnosis. 4. ultrasound screening, the technique is not standard, the cut surface is not standard, the rear of the left atrium is obviously smooth, and the uncai search for its clear cause leads to the occurrence of missed diagnosis [4]. In this case, the image of pregnancy screening in the fetus, the heart image is small, not fully magnified, the color scale is too high, no obvious pulmonary venous blood flow is shown, and no obvious pulmonary venous angle is seen, resulting in missed diagnosis and the occurrence of misdiagnosis. With the standardized management of prenatal ultrasound images, complete ectopic pulmonary vein drainage has received more and more attention, and the detection rate has been significantly improved.