Rh Alloimmunization
Within normal range, no anemia
Did our AI summary help? Let us know.
Evidence-based calculations Used in clinical settings worldwide Regular monitoring recommended
Ready to run the numbers?
Why: This calculation helps assess important health parameters for clinical and personal wellness tracking.
How: Enter your values above and the calculator will apply validated formulas to compute your results.
Run the calculator when you are ready.
✅ Normal MCA-PSV
Within normal range, no anemia
Click to load
⚠️ Borderline Elevated
Approaching 1.5 MoM threshold
Click to load
🔶 Mild Anemia Suspected
MCA-PSV above 1.5 MoM
Click to load
🔴 Severe Anemia Risk
Significantly elevated MCA-PSV
Click to load
🦠 Parvovirus B19 Monitoring
Non-immune cause of anemia
Click to load
MCA-PSV Measurement
Clinical Indication
Additional Information
Fetal History
Previous Measurement (Optional - for trend)
MCA-PSV Reference Chart
Clinical Summary
| Your MCA-PSV | 40 cm/s |
| Median for GA | 36.3 cm/s |
| MoM | 1.1 |
| 1.5 MoM Threshold | 54.5 cm/s |
| Transfusion Likelihood | Low |
Recommendations
For informational purposes only — not medical advice. Consult a healthcare professional before acting on results.
🏥 Health Facts
— WHO
— CDC
What is MCA-PSV? Non-Invasive Fetal Anemia Detection
MCA-PSV (Middle Cerebral Artery Peak Systolic Velocity) is a Doppler ultrasound measurement that assesses blood flow in the fetal brain. When a fetus is anemic, the blood becomes thinner (less viscous), causing it to flow faster. This increased velocity in the middle cerebral artery can be detected before the fetus shows other signs of anemia, making MCA-PSV the gold standard for non-invasive fetal anemia screening.
This test revolutionized the management of Rh-sensitized pregnancies and other conditions causing fetal anemia. Before MCA-PSV, invasive procedures like amniocentesis or cordocentesis were required to assess fetal anemia risk. Now, MCA-PSV allows clinicians to monitor at-risk pregnancies non-invasively and reserve invasive procedures for when intervention is truly needed.
Anemia Detection
Detect fetal anemia before it becomes severe. MCA-PSV can identify moderate-severe anemia with over 95% sensitivity using the 1.5 MoM threshold.
MoM Calculation
Calculate Multiple of Median (MoM) using established reference ranges. Compare your measurement to expected values for gestational age.
Trend Monitoring
Track MCA-PSV over time to identify concerning trends. Rising values may indicate worsening anemia even if still below threshold.
Clinical Guidance
Get recommendations for follow-up intervals and when intervention may be needed. Know when to escalate care to a maternal-fetal medicine specialist.
Transfusion Planning
Understand transfusion likelihood based on MCA-PSV results. Elevated values above 1.5 MoM typically warrant intervention consideration.
How Does MCA-PSV Work? The Science of Doppler Assessment
Why Blood Flows Faster in Anemia
Lower Viscosity
Fewer red cells = thinner blood
Faster Flow
Thinner blood flows more quickly
Higher PSV
Doppler detects increased velocity
MoM Thresholds and Interpretation
Measurement Technique
Identify MCA
Locate the circle of Willis and middle cerebral artery
Correct Angle
Insonation angle should be 0-15 degrees
Sample Proximal
Measure near origin from internal carotid
Fetal Rest
Obtain during fetal quiescence, not breathing
When is MCA-PSV Monitoring Used? Indications and Timing
Rh Alloimmunization
Most common indication. Monitor Rh-negative mothers with anti-D antibodies who are at risk of hemolytic disease of the fetus.
Kell Sensitization
Anti-Kell antibodies can cause severe fetal anemia. MCA-PSV monitoring is essential as titers correlate poorly with severity.
Parvovirus B19
Maternal parvovirus infection can cause fetal anemia. Monitor for 8-12 weeks after infection until resolved.
Twin-Twin Transfusion
TAPS (Twin Anemia-Polycythemia Sequence) causes anemia in donor twin. MCA-PSV helps monitor both twins.
Hydrops Evaluation
When fetal hydrops is detected, MCA-PSV helps determine if anemia is the underlying cause.
Post-Transfusion
After intrauterine transfusion, MCA-PSV monitors for recurrence of anemia, though reliability is reduced.
Monitoring Frequency
MCA-PSV Reference Values and Calculations
MoM Calculation
The median increases with gestational age (approximately 21 cm/s at 18 weeks to 62 cm/s at 38 weeks)
Anemia Detection Threshold
This threshold detects hemoglobin deficit of approximately 4-5 g/dL below normal
Mari Reference Values (cm/s)
Median values from Mari et al. nomogram, widely used reference standard
Frequently Asked Questions About MCA-PSV
Understanding Results
What does an elevated MCA-PSV mean?
An MCA-PSV above 1.5 MoM suggests the fetus may have moderate to severe anemia. The blood is flowing faster because it's thinner (fewer red blood cells). This doesn't confirm anemia but indicates further evaluation (possibly cordocentesis) is needed.
How accurate is MCA-PSV for detecting anemia?
Using the 1.5 MoM threshold, MCA-PSV has greater than 95% sensitivity for detecting moderate-severe anemia (hemoglobin deficit of 4+ g/dL). Specificity is approximately 90%. This makes it an excellent screening tool with few missed cases.
Clinical Management
What happens if my baby needs a transfusion?
Intrauterine transfusion is performed by a maternal-fetal medicine specialist. Under ultrasound guidance, a needle is placed into the umbilical cord and compatible blood is transfused directly to the fetus. Multiple transfusions may be needed throughout pregnancy.
Is MCA-PSV reliable after a transfusion?
MCA-PSV is less reliable after intrauterine transfusion because adult donor blood has different oxygen-carrying properties. The threshold may need to be adjusted, and clinicians often use additional parameters or more frequent monitoring.
Related Calculators
Bishop Score Calculator
Assess cervical readiness and predict labor induction success
HealthFundal Height Calculator
Assess fetal growth through fundal height measurement correlation
HealthhCG Levels Calculator
Analyze hCG progression and doubling time in early pregnancy
HealthNuchal Translucency Calculator
Assess chromosomal abnormality risk from NT ultrasound measurement
HealthA-a Gradient Calculator
Calculate the Alveolar-arterial (A-a) oxygen gradient to assess oxygenation efficiency. Helps differentiate between pulmonary and extrapulmonary causes of...
HealthAdvanced ABI Calculator (Ankle-Brachial Index)
Comprehensive Ankle-Brachial Index calculator with multiple measurement methods, advanced PAD risk assessment, exercise testing capability, cardiovascular...
Health