Ultrasound is not necessary once a week in late pregnancy. Late pregnancy refers to the 28 to 40 weeks of pregnancy, generally in the 28 to 36 weeks every two weeks of obstetric examination, ultrasound to understand the size of fetal development, fetal position, umbilical cord blood flow, amniotic fluid; 36 to 40 weeks of pregnancy need to be every week of obstetric examination, according to the obstetric examination to understand the fetal position, uterine height, abdominal circumference, there is no umbilical cord around the neck, the amount of amniotic fluid, the maturity of the placenta, and so on. In short, during pregnancy, we should pay attention to rest, reasonable diet, avoid exertion, pay attention to fetal movement, and regular obstetric examination; in late pregnancy, we should pay attention to vaginal bleeding, fluid, abdominal pain and fetal movement, and go to the hospital in time if there is any abnormality or other uncomfortable situation.