Middle cerebral artery velocity time integral as a predictor of fetal anemia using fetal hemoglobin Bart's disease as study model.

Abstract

To assess the diagnostic performance of middle cerebral artery (MCA) velocity time integral (VTI) in predicting fetal hemoglobin (Hb) Bart's disease. This was a secondary analysis of data collected prospectively from pregnant women at risk for fetal Hb Bart's disease assessed at 17-22 weeks' gestation, receiving care at the Maternal-Fetal Medicine Unit, Chiang Mai Hospital, Thailand, between January 2008 and December 2023. Each fetus underwent prenatal measurement of MCA peak systolic velocity (PSV) and MCA-VTI. Final diagnosis of Hb Bart's disease was confirmed by Hb typing of cord blood, obtained by cordocentesis. MCA-PSV and MCA-VTI were evaluated both as absolute values and multiples of median (MoM) normalized for gestational age. Diagnostic performance of MCA-PSV and MCA-VTI for predicting fetal Hb Bart's disease was evaluated and compared using area under the receiver-operating-characteristics curve (AUC), sensitivity, specificity and positive and negative predictive values. A total of 485 fetuses at risk for Hb Bart's disease (109 affected, 376 unaffected) met the inclusion criteria. Absolute MCA-VTI values were significantly higher in affected compared with unaffected fetuses (7.9 ± 1.8 vs 5.4 ± 1.3; P < 0.001) as were MoM values (1.5 ± 0.3 vs 1.0 ± 0.2; P < 0.001). The diagnostic performance of MCA-VTI was superior to that of MCA-PSV for detecting fetal anemia due to Hb Bart's disease, with AUCs of 0.877 (95% CI, 0.836-0.917) and 0.898 (95% CI, 0.857-0.938) for absolute MCA-VTI values (in cm) and MCA-VTI MoM, respectively, compared with 0.842 (95% CI, 0.795-0.889) and 0.854 (95% CI, 0.809-0.899) for absolute MCA-PSV values (in cm/s) and MCA-PSV MoM, respectively (P < 0.001). MCA-VTI is more accurate compared with MCA-PSV for predicting fetal Hb Bart's disease, which indirectly reflects anemia. This suggests that MCA-VTI could serve as an alternative or adjunct to MCA-PSV for detecting fetal anemia, particularly in cases of Hb Bart's disease and potentially for other etiologies. © 2025 International Society of Ultrasound in Obstetrics and Gynecology.