Umbilical arterial pulsatility index

Last revised by Joshua Yap ◉ on 6 May 2023

Citation, DOI, disclosures and article data

Citation:

Weerakkody Y, Yap J, Francis T, et al. Umbilical arterial pulsatility index. Reference article, Radiopaedia.org (Accessed on 03 Oct 2023) https://doi.org/10.53347/rID-71455

DOI:

https://doi.org/10.53347/rID-71455

Permalink:

https://radiopaedia.org/articles/71455

rID:

71455

Article created:

7 Oct 2019, Yuranga Weerakkody ◉

Disclosures:

At the time the article was created Yuranga Weerakkody had no recorded disclosures.

View Yuranga Weerakkody's current disclosures

Last revised:

6 May 2023, Joshua Yap ◉

Disclosures:

At the time the article was last revised Joshua Yap had no financial relationships to ineligible companies to disclose.

View Joshua Yap's current disclosures

Revisions:

11 times, by 6 contributors - see full revision history and disclosures

Systems:

Obstetrics

Synonyms:

UA PI
Umbilical artery 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 pulsatility indexes start at higher values and then decrease progressively towards term. This indicates normal placental development, where there is a progressive decrease in the impedance of the umbilical vascular bed to blood flow.