Doppler matrix ua mca Score — Free Online obstetrics Calculator

How it Works

The Vasculature

Umbilical Artery (UA)	Reflects placental resistance. A normal placenta operates as a low-resistance sink. Abnormal resistance increases the Pulsatility Index (PI) and ultimately halts or reverses diastolic flow.
Middle Cerebral Artery (MCA)	Reflects fetal cardiovascular adaptation. Under hypoxic stress, the fetus dilates cerebral vessels ("brain-sparing effect") to maintain CNS oxygenation, which appears as an abnormally low PI on Doppler.

Cerebroplacental Ratio (CPR)

CPR = (MCA-PI) / (UA-PI)

CPR Interpretation

The CPR is an integrated index. A CPR < 1 (or < 5th percentile for gestational age) is highly abnormal. It essentially flags fetuses that have simultaneously high placental resistance AND cerebral vasodilation (the brain-sparing reflex in full swing).

Clinical Pearls

Key Strengths

Identifies placental insufficiency and fetal redistribution of blood flow highly accurately, significantly earlier than overt signs of decompensation (like late decelerations on an NST)

Absent or Reversed End-Diastolic Flow (AEDF/REDF) in the umbilical artery are definitive, objective, universally agreed-upon triggers for heavy clinical intervention

Known Technical Limitations

Highly angle-dependent: Accuracy evaporates if the angle of insonation exceeds 30° mathematically (close to 0° is strictly required for ideal MCA velocities)

Measurements must exclusively be taken during fetal apnea and absent gross motor movements, as fetal breathing dramatically distorts the waveform

Cannot be interpreted independently of customized, gestational-age-specific nomograms

Next Steps

Umbilical Artery PI > 95th Percentile

01

Identifies established Fetal Growth Restriction (FGR)

02

Increase surveillance frequency (e.g., weekly Dopplers, BPP)

03

Administer maternal corticosteroids for fetal lung maturity if delivery is anticipated preterm

UA Absent/Reversed End-Diastolic Flow (AEDF/REDF)

01

Signifies critical placental failure

02

Admit to hospital for continuous or extremely frequent fetal monitoring

03

Plan for emergent delivery depending on exact gestational age, steroid coverage, and fetal biophysical profile limits

MCA-PI < 5th Percentile (Brain-Sparing)

01

Signals chronic hypoxia and fetal auto-redistribution

02

In late-onset FGR (typically near term), an isolated low MCA-PI strongly prompts delivery even if the umbilical artery is technically normal

The Evidence

Guidelines

Fetal Medicine Foundation protocols established the paradigm of Doppler integration. Modern SMFM guidelines strongly endorse relying upon rigorous UA Doppler over arbitrary biometry cutoffs to sequence delivery in FGR.

Origins & History

Physics Application

Relying upon the Doppler Effect (first described by Christian Doppler in 1842), ultrasound waves bouncing off moving erythrocytes in fetal vasculature change frequency proportionally to blood velocity, allowing modern computers to build precise mathematical resistive indices without invading the uterus.

Doppler Matrix (UA/MCA)

Doppler Surveillance Matrix

When to Use

Primary Clinical Uses

When NOT to Use

How it Works

The Vasculature

Cerebroplacental Ratio (CPR)

CPR Interpretation

Clinical Pearls

Key Strengths

Known Technical Limitations

Next Steps

Umbilical Artery PI > 95th Percentile

UA Absent/Reversed End-Diastolic Flow (AEDF/REDF)

MCA-PI < 5th Percentile (Brain-Sparing)

The Evidence

Guidelines

Origins & History

Physics Application

In Recent Clinical News

Doppler Matrix (UA/MCA)

Doppler Surveillance Matrix

When to Use

Primary Clinical Uses

When NOT to Use

How it Works

The Vasculature

Cerebroplacental Ratio (CPR)

CPR Interpretation

Clinical Pearls

Key Strengths

Known Technical Limitations

Next Steps

Umbilical Artery PI > 95th Percentile

UA Absent/Reversed End-Diastolic Flow (AEDF/REDF)

MCA-PI < 5th Percentile (Brain-Sparing)

The Evidence

Guidelines

Origins & History

Physics Application

In Recent Clinical News