Ultrasound is accurate for fetal size, especially in early pregnancy, and it is very accurate for us to measure the fetus by early pregnancy ultrasound to estimate its gestational week size, but in late pregnancy at full term, there may be some small errors in the ultrasound assessment of fetal size. This is because at full term, the fetus’ bones and limbs are well developed, and its position and space are restricted, so it is not easy to make some of our measurement cuts at this time to be particularly standard. So the error of measurement at full term will be there, and this error will be a bit larger, which is acceptable, but accurate in the early stage. Because we have some pregnant mothers who have messy menstrual stoppage and their periods are not good, the gestational week is also judged based on the results of early pregnancy ultrasound to correct and infer the gestational week. So the ultrasound measurements are still accurate in the early stages, provided of course that the ultrasonographer’s cut and measurements are standard.