MCA Calculator
Assess fetal anemia risk using Middle Cerebral Artery Doppler measurements
Calculate MCA Measurements
Valid range: 15-42 weeks
Measured during fetal Doppler ultrasound examination
Example Calculation
Normal Pregnancy at 28 Weeks
Gestational age: 28 weeks
Measured MCA PSV: 35.2 cm/s
Median PSV calculation: log(PSV) = 2.31 + 0.046 x 28 = 3.598
Median PSV: 10^3.598 = 39.6 cm/s
Result
MoM: 35.2 ÷ 39.6 = 0.89
Risk assessment: Low risk for fetal anemia (MoM <1.29)
Recommendation: Continue routine prenatal care
MCA Doppler Applications
Fetal Anemia
Primary screening tool
Rh isoimmunization, parvovirus B19
Growth Restriction
Fetal hypoxia assessment
Brain-sparing circulation
Twin Pregnancies
TTTS monitoring
Twin-to-twin transfusion syndrome
Preeclampsia
Risk assessment
Maternal vascular disease
MCA Reference Values
Key Points:
- • Angle correction: 0-15° optimal
- • Sample gate: 1-2mm
- • Proximal MCA measurement preferred
- • Multiple measurements recommended
Understanding MCA Doppler Assessment
What is MCA Doppler?
Middle Cerebral Artery (MCA) Doppler ultrasound measures blood flow velocity in the fetal brain's main artery. It's a non-invasive method to assess fetal well-being, particularly for detecting fetal anemia and evaluating cerebral blood flow patterns.
Clinical Applications
- •Screening for fetal anemia (Rh disease, parvovirus B19)
- •Assessment of fetal hypoxia and growth restriction
- •Monitoring twin-to-twin transfusion syndrome
- •Evaluation of maternal diabetes effects
Mari Formula
log(MCA PSV) = 2.31 + 0.046 x GA
- PSV: Peak Systolic Velocity (cm/s)
- GA: Gestational Age (weeks)
- MoM: Multiple of Median (measured/expected)
Technical Considerations
Important: MCA Doppler should be interpreted alongside complete fetal biometry, amniotic fluid assessment, and maternal clinical history.