MCA Peak Systolic Velocity Calculator

Enter gestational age and the observed MCA peak systolic velocity (PSV) to compute the expected median PSV and multiples of median (MoM).

weeks
Risk alert: MoM ≥ 1.5
Median MCA PSV
Multiples of Median (MoM)

The formula used: PSV = e^(2.31 + 0.04643 × GA). Confirm clinical interpretation before acting. MoM ≥ 1.5 indicates higher risk of fetal anemia.

Technique

  • Fetus should be at rest without breathing or body movements.
  • Obtain an axial view of the fetal head and identify the Circle of Willis with color Doppler (Image A).
  • Enlarge the MCA so it occupies ≥ 50% of the screen; use 1 mm sample volume placed ~2 mm from MCA origin from the internal carotid artery (Image B).
  • Align the ultrasound beam parallel to flow (angle ≈ 0°) and record the highest PSV; repeat measurement at least 3 times.