Performance of middle cerebral artery doppler for prediction of recurrent fetal anemia

Objective: To assess the predictive value of middle cerebral artery Doppler peak systolic velocity (MCA-PSV) for moderate-severe fetal anemia following one intrauterine transfusion (IUT) and test the performance of alternate cutoffs to the recommended threshold ≥1.69 multiples of the median (MoM). Methods: This was a retrospective cohort study of patients with pregnancies affected by alloimmunization who underwent percutaneous umbilical blood sampling (PUBS) procedures from 2000 to 2020. An MCA-PSV ≥1.69 MoM was the indication for the second IUT. The primary outcome was recurrent moderate-severe fetal anemia. Receiver-operating characteristic (ROC) curves assessed the predictive ability of MCA-PSV for the primary outcome and the Youden index identified the “optimal” cutoff value. Predictive characteristics of MCA-PSV ≥1.69 MoM and the “optimal” cutoff were compared. Results: Of the 58 patients who underwent IUT during the study period, 36 (62%) did not meet inclusion criteria. Of the remaining 22 patients who underwent a second PUBS, 12 (54.6%) fetuses had moderate or severe anemia. Following one IUT, the AUC for MCA-PSV was 0.86 (95% CI 0.70–1.00) for the primary outcome. The “optimal” cutoff MCA-PSV value was 1.74 MoM, which had a greater specificity than ≥1.69 MoM (90 vs. 50%, p =.05), but was not statistically significant. The sensitivity was similar between the two cutoff values of ≥1.69 and ≥1.74 MoM (83.3 vs. 75.0%, p =.65) (Table 2). Conclusion: Raising the recommended MCA-PSV cutoff to ≥1.74 MoM for recurrent moderate-severe fetal anemia after one IUT would decrease the number of unnecessary procedures without significantly changing the sensitivity of this screening test.