The main reference to the large examination is the four-dimensional ultrasound examination in mid-pregnancy, the price varies from region to region, generally around 500 to 700 yuan. The purpose of the examination is to observe the growth and development of the fetus, and to determine whether there is any malformation in the reproductive development of the fetus in a more comprehensive manner. The most common examination is the four-dimensional ultrasound, which can clearly and three-dimensionally display the organs of the fetus, dynamically monitor the physical condition of the fetus, and detect developmental malformations, such as Down’s Syndrome. The cost of this test is between $500 and $800 and may fluctuate. The major screening test is usually performed between 20 to 28 weeks of pregnancy. Pregnant women are advised to visit the hospital in a timely manner and under the guidance of the doctor to have a reasonable examination, and if there are abnormalities, timely intervention measures should be taken.