Secondary screening is usually performed at 28-32 weeks of pregnancy. Through ultrasound examination, it can show all parts of the fetal organs, so as to understand the growth and development of the fetus, observe the head, limbs and the general structure of each organ, such as whether there are malformations in the development of the heart, lungs and brain. In addition, the second screening can also understand the fetal position, the position and maturity of the placenta, and the condition of amniotic fluid, which can guide the mode of delivery. Before the screening, you can take a walk or take the stairs to make the fetus in the best position, which can make the test results clearer and reduce errors. If the test result shows that the fetus is small, it is necessary for the pregnant woman to strengthen nutritional supplements and gain weight appropriately. If the fetus is too large, attention should be paid to adjust the nutritional structure and control the weight so as not to affect the delivery. During pregnancy, you should pay attention to regular maternity checkups to keep abreast of the fetal development. Pay attention to maintain a balanced nutrition in daily life and avoid overworking. Stay away from radiation, harmful substances and other places, and increase physical activity appropriately, which is beneficial to the fetal development.