The fetal PI value is an indicator of fetal umbilical artery blood flow, which checks the blood supply to the fetal umbilical artery and reflects the proportional relationship between the magnitude of the decrease in blood flow velocity and the average velocity of the heart during diastole. The PI value varies at different weeks of gestation. At 24 weeks of pregnancy, this average value is 3.5 and the upper limit is 4.25, above or below this range is abnormal. This indicator is also important to check for intrauterine growth retardation, or hypertension during pregnancy, intrauterine hypoxia and congenital developmental abnormalities, chromosomal abnormalities, etc. If you suspect fetal umbilical blood flow abnormalities, pay attention to fetal movement and take the left side position when sleeping. If there is intrauterine hypoxia, there may be frequent fetal movements and increased fetal heart rate, which may require hospitalization for fetal preservation and observation.