Obstetric ultrasound is the key item in 28 weeks of pregnancy, in addition, it also includes some routine checkups, such as blood routine, urine routine, leukorrhea routine, electrocardiogram and so on. 1. Obstetric ultrasound is mainly carried out during the 24-28 weeks of pregnancy. If the previous pregnancy checkup has already done an obstetric ultrasound (3D or 4D), then this time a routine obstetric ultrasound checkup will be done, and at the same time, weight, uterine height, and abdominal circumference will be measured, through which you can continue to observe the physical development of the fetus, and listen to the frequency of the fetal heartbeat. 2. In addition to the 3D or 4D ultrasound, there are other routine checkups, such as routine blood test, urine test, electrocardiogram, and routine leukorrhea test. Blood test to check for anemia and infection; urine test to check for urinary tract infection and gestational hypertension; electrocardiogram to assess heart function; and leukorrhea test to check for vaginitis. In addition to these tests, if the pregnant woman has other underlying diseases, she needs to be evaluated accordingly, and her obstetrician will decide what kind of tests to do according to her condition.