Middle cerebral artery peak systolic velocity (MCA-PSV) is used in Rh isoimmunised pregnancies. Which MCA-PSV threshold triggers fetal blood sampling and possible intrauterine transfusion?
- A MCA-PSV >1.5 MoM ✓
- B MCA-PSV >1.0 MoM
- C MCA-PSV >2.0 MoM
- D MCA-PSV >1.25 MoM
Correct answer: A. MCA-PSV >1.5 MoM
Explanation
MCA-PSV >1.5 MoM (multiples of the median) for gestational age is the threshold that predicts moderate-to-severe fetal anaemia with high sensitivity and specificity (Mari et al., NEJM 2000). Values above this threshold prompt cordocentesis (fetal blood sampling) and, if confirmed anaemic (fetal Hct <30%), intrauterine transfusion. This threshold replaced invasive amniocentesis for bilirubin measurement (deltaDO450) as the standard monitoring tool.
Reference: Williams Obstetrics, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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