The umbilical artery pulsatility index (UAPI) can be measured from the blood flow in the umbilical arteries using Doppler ultrasonography. This can be used to evaluate a high risk pregnancy and monitored over time.


The flow measurements should be taken in both umbilical arteries.



(1) peak systolic velocity (PSV)

(2) end-diastolic velocity (EDV)

(3) time-averaged mean velocity (TMAX)


pulsatility index =

= ((peak systolic velocity) - (end-diastolic velocity)) / (time-averaged mean velocity)


The location along the cord should be recorded - periplacental, free loop, or peri-vesical. The value near the placental is usually the lowest and the value near the umbilicus the highest. The mean pulsatility index near the umbilicus was 1.07 with SD 0.19.


difference between the two umbilical arteries =

= ((PI in first) - (PI in second)) / (PI in second) * 100


To read more or access our algorithms and calculators, please log in or register.