A high umbilical cord blood flow S/D value in the second trimester of pregnancy indicates that the fetus may have conditions such as intrauterine hypoxia and does not indicate a Down’s baby. Measurement of umbilical cord blood flow S/D value can reflect the blood perfusion of the placenta. In late pregnancy, the S/D of umbilical cord blood flow is usually less than 3. If the value is greater than 3, it only indicates that the fetus may have intrauterine hypoxia, which is not related to Down’s syndrome. If the value is not greater than 3, but just on the high side, then the fetus is usually normal. It is recommended that once the patient has a high S/D in the umbilical cord blood flow in the second trimester of pregnancy, he/she should not be too anxious, relax and pay attention to the number of fetal movements, if the number of movements increases significantly, consult the doctor in time, in order to prevent fetal hypoxia and intrauterine death.