In the ultrasound examination of pregnant women, HC represents the fetal head circumference, which is the distance from the root of the forehead to the occipital ridge of the back of the head. The fetal head circumference is the distance from the root of the forehead to the occipital ridge of the back of the head. The fetal head circumference increases with the gestational week, but the results are usually within the normal range to indicate normal fetal growth. If the fetal head circumference differs from the normal head circumference of the pregnant woman by more than 2 weeks, it is possible that the fetus has abnormal growth. In general, when the fetal head circumference is small, the presence of malformation, chromosomal abnormality, malnutrition, etc. should be considered, while when the fetal head circumference is large, the presence of hydrocephalus, overnutrition and other abnormalities in cranial development should be considered. In this case, we should first go to the eugenics and genetics department for relevant examination to observe whether the fetus has intracranial structural dysplasia, and if this is ruled out, we can adjust the pregnant woman’s diet to restore the normal nutritional development of the fetus.