Umbilical arterial pulsatility index

Umbilical arterial pulsatility index (UA-PI) is a parameter used in umbilical arterial (UA) Doppler assessment It is calculated by subtracting the end-diastolic velocity (EDV) from the peak systolic velocity (PSV) and then dividing by the time-averaged (mean) velocity (TAV):

  • PI = (PSV - EDV) / TAV

Practical points

Reference ranges depend on the stage of gestation. In normal pregnancies, umbilical arterial PI starts at higher values and then decreases progressively towards term. This indicates that normal in placental development, there is a progressive decrease in the impedance of the umbilical vascular bed to blood flow.

See also

Share article

Article information

rID: 71455
System: Obstetrics
Synonyms or Alternate Spellings:
  • Umbilical artery pulsatility index
  • UA PI

Support Radiopaedia and see fewer ads

Updating… Please wait.

 Unable to process the form. Check for errors and try again.

 Thank you for updating your details.