In early pregnancy, the number of gestational weeks can be calculated based on the size of the gestational sac detected by ultrasound. Usually, taking the head-rump diameter before 6 or 7 weeks is an accurate method, and the average of 3 measurements is usually taken, and the formula for projecting the gestational weeks by ultrasound in early pregnancy is: gestational weeks = germ or head-rump diameter length + 6.5, for example, the ultrasound result shows that the value of the fetus’ head-rump diameter is 0.5cm, then 0.5 + 6.5 = 7, which means that at this time the This means that the gestational week is around seven weeks. In the second and third trimesters, the calculation can be based on the biparietal diameter, head circumference and abdominal circumference of the fetus, combined with the length of the femur. However, because the size of the fetus in the later stages is affected by the nutritional status of the mother and other factors, the data may be incorrect. If the ultrasound calculation and the actual gestational week do not match, the fetus may have developmental delay or overgrowth, which needs to be corrected in time: 1. Developmental delay: Patients can take or inject nutritional drugs under the guidance of doctors to unblock microcirculation and promote fetal development. In addition, in the daily diet, more protein-rich foods, such as eggs, milk, etc., can be consumed to supplement the nutrition of the patient and the fetus; 2, overgrowth: mostly caused by excessive dietary intake or too little activity, the patient should reduce the intake of high-carbohydrate, high-fat diet, especially high-carbohydrate type, such as common steamed buns, rolls, porridge, etc.; at the same time, the patient should, according to their own situation, moderately increase Exercise. Patients are advised to eat a light diet, eat less and more meals, and can eat more vitamin-rich foods such as oranges and kiwis to replenish the body’s required nutrients.