The seventh trimester fetus is equivalent to 28 weeks of gestation. This is the period when the second level prenatal ultrasound, also known clinically as systematic screening, is performed between 28 and 32 weeks of gestation, and is one of the screening programs for fetal malformations in late pregnancy. At 28 weeks of gestation, which is the early stage of late pregnancy, the ultrasound examination firstly needs to detect various biological data of the fetus and determine whether the fetus conforms to the actual number of weeks of gestation, and at this time, all the examination items are basically the same as the 4D ultrasound examination at the third level, except for the six serious structural malformations of the fetus as stipulated by the national health department. In addition, the development of the fetal heart structure has been perfected during this period, and the anatomical structure of the fetal heart can be clearly displayed when the fetus is in a good position. Although the ultrasound examination of the fetus is more comprehensive during this period, there are still many factors that may affect the anatomy of some tissues and organs. It is important to note that if there are abnormalities in the previous ultrasound examination, the ultrasonographer must be prompted to focus on them during the second examination. Also, because the examination time is longer than other ultrasound procedures, it is important to inform the ultrasound doctor in a timely manner if there is any discomfort.