28-32 weeks is the imaging examination to observe the fetus in the late pregnancy, generally refers to the detoxification ultrasound, the main contents of the examination are fetal growth and development, fetal position, amniotic fluid volume, placental position, etc. Through the examination, the results of the major detoxification examination can be reviewed and the probability of abnormal fetus being screened out can be improved. 1. fetal growth and development: the detoxification ultrasound can be used to 2.Fetal position: 28-32 weeks of pregnancy is the best time to correct the fetal position, and the ultrasound can check whether there are problems such as fetal malposition and umbilical cord encirclement, and if there is, it can be corrected early; 3.Amniotic fluid volume: because too much or too little amniotic fluid may lead to serious complications, fetal malformation and premature birth, so the ultrasound can avoid 4. Placenta position: If placenta praevia or low placenta appears in late pregnancy, it may lead to bleeding and prevent normal delivery of the fetus, so the abnormal position of placenta can be found through ultrasound. Pregnant women can take a proper walk before the screening ultrasound to promote the baby’s movement in the abdomen, which may help the doctor to get a multi-angle observation. Before and after the examination and during the examination, pregnant women should also put their mind at ease, keep a relaxed mood, pay attention to rest and avoid excessive fatigue.