The normal range of S/D of the umbilical artery at 31 weeks is 2.22-3. The umbilical artery value is the ratio of systolic to diastolic blood flow in the umbilical artery, or S/D value. The umbilical artery value mainly reflects whether the fetus is at risk of intrauterine hypoxia. Normally as the weeks of pregnancy increase, the umbilical artery value will be smaller, 3 weeks umbilical artery SD normal value is usually no more than 3.0 weeks umbilical artery value S / D range is 2.22-3. When the umbilical artery value is greater than 3.0 at 31 weeks of gestation, intrauterine hypoxia may be present and fetal heart rate monitoring is required. When the umbilical artery value is too low, the placenta may not be supplying enough nutrients. Review the obstetric ultrasound to see if there is intrauterine growth restriction and strengthen the nutritional supplements. Pregnant women should pay attention to the prenatal examination during pregnancy, actively listen to the professional doctor’s advice to do a comprehensive nursing care, pay attention to more rest, at the same time, should relax, avoid tension, anxiety, any discomfort should be timely to the hospital, by the doctor to clarify the diagnosis, and cooperate with the doctor to deal with the symptoms.