At 35 weeks of pregnancy, the normal range of fetal head circumference is 293-330mm, and the standard value is 312mm, which varies from person to person, and the fetal development can be effectively judged by head circumference: if there is abnormal head circumference diameter, first of all, we need to combine menstruation and early pregnancy ultrasound results, check the gestational week, review medical records, determine the gestational week and growth rate of fetal head circumference increase, combine with the biparietal diameter, abdominal circumference and femur length. If the fetus has a large biparietal diameter and head circumference and is progressively increasing, and the abdominal circumference is normal or small, the fetus should be consulted by prenatal diagnostic institutions to rule out hydrocephalus; if the fetus has a small biparietal diameter and head circumference and is growing slowly, the fetus should be consulted by prenatal diagnostic institutions to rule out hydrocephalus, etc. If the fetus is small in both parietal diameter and head circumference, the fetus is slow in growth, and the fetal cranial development should be detected by fetal cranial MRI. The fetal growth retardation is caused by chromosomal abnormalities, infections, maternal hypertension, diabetes mellitus, heart disease, nail function abnormalities, immune disorders, embolism, etc. The fetal growth retardation can be treated with nutritional support and vitamin and protein rich foods, such as spinach, celery, milk, eggs, etc., to supplement the nutrients that are lacking in the human body and facilitate fetal growth. In addition to hereditary factors, we should consider over-nutrition or gestational diabetes, especially for women with excessive amniotic fluid and recurrent mycosis fungoides, even if the results of glucose tolerance are normal, we should review the blood sugar to exclude the fetus from being large due to high blood sugar. In addition, pregnant women should go to the nutrition clinic during pregnancy, receive standardized dietary guidance, eat a divided diet, avoid eating too much high-calorie food, such as sugary food and fruits, and combine with moderate exercise to control fetal weight gain. The fetus changes rapidly in the second trimester, so it is necessary to strengthen maternity checkups, pay attention to fetal movement, and go to the hospital promptly if there is abnormal fetal movement.