A fetus that is two weeks small does not necessarily mean that it is not developing normally, and the cause needs to be identified under the supervision of a doctor. Ultrasound indicates that the fetus is two weeks small, the first step is to check the actual gestational week, from the last menstrual period, early pregnancy ultrasound to confirm that the gestational week is correct before proceeding to the next step of screening. Fetal growth restriction should be considered if the ultrasound gestational week is less than 2 weeks from the actual gestational week and requires close observation and further screening. Possible causes of fetal growth restriction include the mother, fetus, placenta and umbilical cord. 1. Maternal causes: including malnutrition, gestational diabetes mellitus, renal disease, heart disease, thyroid disease, autoimmune disease, gestational hypertension, gestational intrahepatic cholestasis, multiple births. 2. Fetal anomalies: including genetic abnormalities (genetic, chromosomal abnormalities) and structural abnormalities. 3. Placental anomalies: including placental hemangioma, small placenta, etc. 4. Umbilical cord anomalies: including single umbilical artery, umbilical cord too thin, umbilical cord torsion, kinking, etc. In addition, there are other factors reasonable prenatal examination can be early detection of fetal anomalies, but when the ultrasound examination suggests that the fetus is 2 weeks small is not necessarily on behalf of the development is not normal, may be related to genetic, nutritional and other reasons, does not necessarily affect the structure of fetal organs and dysfunction, can be under the guidance of the doctor active nutritional supportive therapy.