Management of Kell isoimmunization - Evaluation of a Doppler-guided approach

Objective: To assess the role of peak systolic velocity in the middle cerebral artery (MCA-PSV) in the management of pregnancies complicated by Kell isoimmunization. Methods: Sixteen fetuses were monitored by conventional protocol (Group 1) and eight fetuses by an MCA-PSV-guided protocol (Group 2). The conventional protocol included a weekly ultrasound evaluation and measurement of maternal anti-Kell titers every 4-6 weeks. In Group 2 Doppler assessment of the MCA-PSV was performed at intervals of 4 to 7 days and MCA-PSV > 1.5 multiples of the median (MoM) was considered as an indication for fetal blood sampling (FBS). Results: No parameter emerged as a reliable predictor of isoimmunization severity in Group 1. In Group 2, no FBS was necessary in one case since the MCA-PSV values obtained during the follow-up were < 1.29 MoM. In two cases the first FBS was already indicated after 1 week of follow-up, but five other fetuses were followed for 3-9 weeks before FBS was indicated. All fetuses with MCA-PSV > 1.5 MoM prior to intrauterine transfusion (IUT) had severe fetal anemia on FBS. In fetuses with severe anemia on the first FBS, the MCA-PSV values 7 days before the first FBS were < 1.29 MoM (four cases), between 1.29 and 1.5 MoM (two cases) and > 1.55 MoM (one case). Conclusions: In the management of Kell isoimmunization invasive procedures may be avoided by implementing MCA-PSV measurements. Delineation of appropriate intervals between reassessments, the reliability of MCA-PSV following repeated IUTs, and cut-off values for FBS await further study.