MCA Calculator (Middle Cerebral Artery)

MCA Calculator (Middle Cerebral Artery). Enter your gestational age (in weeks and days) and the MCA Peak Systolic Velocity measured during your ultrasound to assess fetal anemia risk. The MCA Calculator computes the median MCA PSV for the given gestational age, the Multiple of Median (MoM) value, and an interpretation of the anemia risk level — helping clinicians evaluate whether the fetal blood flow speed is within a normal range. Also try the find CHA2DS2-VASc Score with CHA2DS2-VASc Score Calculator.

Results

MoM (Multiple of Median)

Median MCA PSV for Gestational Age

Anemia Risk Assessment

Gestational Age Used

What is the MCA calculator used for?

The MCA (Middle Cerebral Artery) calculator is used to assess the risk of fetal anemia during pregnancy. It calculates the Multiple of Median (MoM) based on the measured MCA Peak Systolic Velocity and the gestational age, helping clinicians decide whether further investigation or intervention may be needed. See also our PERC Calculator.

What is MCA Peak Systolic Velocity (PSV)?

MCA Peak Systolic Velocity is the maximum speed of blood flow measured in the fetal middle cerebral artery during a Doppler ultrasound. When a fetus is anemic, its blood becomes thinner and flows faster, so an elevated PSV can indicate possible fetal anemia without the need for invasive testing.

What does MoM mean in the MCA calculator?

MoM stands for Multiple of Median. It represents the ratio of the measured MCA PSV to the expected median MCA PSV for that gestational age. A MoM above 1.5 is generally considered indicative of moderate-to-severe fetal anemia and typically prompts further clinical evaluation.

How is the median MCA PSV calculated?

The median MCA PSV is derived from the established Mari et al. formula: log(MCA PSV) = 2.31 + 0.046 × gestational age (in weeks). This gives the expected median velocity for a given gestational age, against which the measured PSV is compared.

At what MoM value is fetal anemia suspected?

A MoM value of 1.5 or higher is the widely accepted clinical threshold for suspecting moderate-to-severe fetal anemia. Values between 1.29 and 1.49 MoM are considered mildly elevated, while values below 1.29 MoM are generally within the normal range.

Between which gestational ages can MCA Doppler be used reliably?

MCA Doppler assessment for fetal anemia is most reliable between approximately 14 and 40 weeks of gestation. The technique is routinely used in monitoring pregnancies complicated by red blood cell alloimmunization or other conditions associated with fetal anemia risk.

Can this calculator replace a doctor's assessment?

No. This calculator is intended as a clinical support tool and should never replace a qualified physician's judgment. MCA Doppler results must always be interpreted in the context of the full clinical picture, including maternal antibody levels, fetal biophysical profile, and obstetric history.

Why is the middle cerebral artery used to detect fetal anemia?

The middle cerebral artery is one of the major vessels supplying the fetal brain. Because the brain is a priority organ, anemia causes compensatory redistribution of blood flow, increasing velocity in the MCA. This makes the MCA PSV a sensitive and non-invasive marker for fetal anemia detection. You might also find our calculate Aortic Valve Area AVA (Continuity Equation) useful.