Select a vessel and GA to see typical PI/RI/PSV ranges and whether your value is below, within, or above the band.

How to use this calculator

Choose the vessel (Umbilical artery or MCA) and Doppler measure (PI, RI, or PSV).
Enter gestational age (weeks+days). Optional: add your measured value.
Tap Lookup to see the typical band for that GA and how your value compares.

PI/RI are unitless; PSV is usually reported in cm/s.

Methodology and sources

What this tool shows

A broad, gestation-specific reference band for the selected vessel (umbilical artery or middle cerebral artery) and Doppler measure (PI, RI, or PSV).
An optional comparison of your entered value against that band with a simple note (below / within / above typical).

How the ranges are generated

Weeks are grouped into short intervals (e.g., 18–22, 23–27) that reflect the usual downward trend of UA PI/RI with advancing gestation and the characteristic MCA profiles used in practice.
For each interval, the tool presents a rounded “typical” low–high band derived from commonly cited reference tables. PI and RI are unitless; PSV is shown in cm/s.
Inputs are clamped to practical use (≈16–40 weeks). Outputs are rounded for readability (0–2 decimal places depending on measure).

Scope and limits

Values are for quick orientation and counselling. Clinical interpretation depends on full ultrasound context (machine presets, sampling technique, fetal state) and local percentiles/MoM thresholds.
Management commonly follows guideline frameworks for growth restriction and anemia surveillance (e.g., UA Doppler in FGR pathways; MCA-PSV for fetal anemia). Always use local protocols.

Sources

ACOG Practice Bulletin: Fetal Growth Restriction (use of UA Doppler in surveillance). acog.org/.../fetal-growth-restriction
ISUOG Practice Guidelines (updated): use of Doppler velocimetry in obstetrics (UA/MCA reference use and clinical application). openaccess.sgul.ac.uk/id/eprint/113549/

Last updated: 6 Oct 2025

Support if you have experienced a loss

Reading about miscarriage, stillbirth, or infant loss can be difficult. If you have experienced a loss, you do not have to use this calculator or read the statistics. You may find it more helpful to talk with your care team or a support organization.

In the United States, groups such as:

offer information and bereavement support. If you are elsewhere, your local health service or a pregnancy and baby loss charity may be able to guide you to support in your region.