A Rh-negative sensitised woman is followed from 20 weeks for suspected fetal anaemia. Which Doppler parameter is used as the primary noninvasive screening test for severe fetal anaemia?
- A Umbilical artery systolic-diastolic ratio
- B Ductus venosus pulsatility index
- C Middle cerebral artery peak systolic velocity ✓
- D Middle cerebral artery resistance index
Correct answer: C. Middle cerebral artery peak systolic velocity
Explanation
Anaemic fetuses maintain oxygen delivery by increasing cardiac output, which raises blood velocity, so a middle cerebral artery peak systolic velocity above 1.5 multiples of the median for gestational age predicts moderate to severe anaemia and triggers cordocentesis or intrauterine transfusion. Umbilical artery indices reflect placental resistance, and ductus venosus waveforms reflect cardiac compromise, neither of which tracks haemoglobin concentration directly.
Reference: Williams Obstetrics, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.