Flowcytometric assessment of fetomaternal hemorrhage during external cephalic version at term.

External cephalic version (ECV) at term is a safe procedure and reduces the incidence of cesarean sections for breech presentation. One of the known complications, however, is an ECV-related disruption of the placental barrier and a subsequent transfusion of fetal blood into maternal circulation. While the incidence of ECV-related fetomaternal hemorrhage (FMH) has been determined recently in a large trial using a manual Kleihauer-Betke test (KBT), questions remain on the amount of ECV-related FMH. KBT, which detects fetal red blood cells (RBC) on the basis of acidic resistance of fetal hemoglobin (HbF), is known to be a sensitive test, yet prone to procedural errors limiting its accuracy in quantifying FMH. In this study we investigated 50 patients for FMH before and after ECV, using a dual-color flow cytometric test kit with a lower limit of quantification of 0.05% fetal RBC in maternal peripheral blood. Three patients had a quantifiable increase of fetal RBC detected after ECV (0.06%; 0.08%; 0.1%). None of these subtle increments was predictable by ECV-related clinical parameters or translated into fetal compromise. Using a sensitive and accurate flow cytometric test method, our data provide further assurance to mothers on the safety of ECV at term.