What is the normal value of umbilical artery resistance index

The normal value of the umbilical artery resistance index UA-RI is generally between 0.6-0.8, and the actual value is influenced by factors such as gestational age, fetal activity status, and placental function. Monitoring UA-RI during pregnancy can evaluate the intrauterine blood supply to the fetus, and abnormal elevation may indicate placental dysfunction or fetal distress.

1. Influence of gestational age:

UA-RI shows a decreasing trend with increasing gestational age. The upper limit of normal value can reach 0.9 before 24 weeks of pregnancy, and it stabilizes in the range of 0.6-0.8 after 30 weeks of pregnancy. In late pregnancy, if the RI value remains above 0.8, it is necessary to be alert to insufficient placental blood flow perfusion.

2. Measurement timing:

It is recommended to choose the interval between fetal movements for measurement. When the fetus undergoes respiratory movements or frequent fetal movements, the RI value may briefly increase by 0.1-0.2, and repeated measurements are needed to obtain a stable value.

3. Placental factors:

When placental villi are poorly developed or infarcted, UA-RI can increase to 0.9 or above. This condition is often accompanied by abnormal uterine artery blood flow and requires ultrasound evaluation of placental morphology.

4. Fetal condition:

During intrauterine hypoxia, peripheral vascular constriction can lead to an increase in UA-RI. If there is a loss or reversal of diastolic blood flow, it indicates severe hypoxia and requires emergency intervention.

5. Maternal diseases:

Hypertension during pregnancy, diabetes and other diseases may cause placental vascular diseases. When maternal blood pressure control is poor, UA-RI values are often higher than the average level of the same gestational week.

It is recommended that pregnant women maintain a left lateral position to improve placental blood flow and monitor fetal movement changes daily. After 28 weeks of pregnancy, fetal heart rate monitoring should be performed weekly. If fetal movement is reduced or UA-RI remains high, timely follow-up ultrasound should be performed. Pay attention to supplementing high-quality protein and iron elements in diet, and avoid prolonged standing or vigorous exercise. For pregnant women with pregnancy complications, it is necessary to follow medical advice to increase the frequency of prenatal check ups and, if necessary, be hospitalized for observation.