In Rh isoimmunized pregnancy, which parameter measured by Doppler ultrasound is used as the PRIMARY non-invasive surveillance tool to assess fetal anaemia?

• A Umbilical artery systolic/diastolic ratio
• B Middle cerebral artery peak systolic velocity (MCA-PSV) ✓
• C Ductus venosus pulsatility index for veins (PIV)
• D Biophysical profile score

Explanation

MCA-PSV (middle cerebral artery peak systolic velocity) has replaced amniocentesis for ΔOD450 as the primary non-invasive tool for detecting fetal anaemia in alloimmunized pregnancies. An MCA-PSV > 1.5 multiples of the median (MoM) for gestational age is the threshold for fetal blood sampling/intrauterine transfusion. This is based on the principle that anaemic fetuses have increased cardiac output and reduced blood viscosity, increasing MCA-PSV.

Reference: Williams Obstetrics, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.