Middle cerebral artery (MCA) peak systolic velocity (PSV) Doppler is used to screen for fetal anaemia in Rh-isoimmunized pregnancies. Which MCA-PSV threshold (in multiples of median, MoM) is used to diagnose moderate-to-severe fetal anaemia and guide the decision for intrauterine transfusion?
- A MCA-PSV >1.5 MoM ✓
- B MCA-PSV >1.29 MoM
- C MCA-PSV >1.8 MoM
- D MCA-PSV >2.0 MoM
Correct answer: A. MCA-PSV >1.5 MoM
Explanation
The landmark study by Mari et al. (NEJM 2000) established that MCA-PSV >1.5 MoM predicts moderate-to-severe fetal anaemia with a sensitivity of 100% and a false positive rate of 12%. Values >1.5 MoM indicate fetal haematocrit likely <30% and are the threshold for cordocentesis and intrauterine transfusion consideration. This has largely replaced amniocentesis (AOD450) for managing Rh-isoimmunized pregnancies. The 1.29 MoM threshold was used in earlier amniocentesis-based practice.
Reference: Williams Obstetrics, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.