Two-way trafficking of Annexin V positive cells between mother and fetus: determination of apoptosis at delivery

Objectives The aim of this study was to quantitate apoptosis in maternal circulation and umbilical cord blood (UCB) at delivery. The proportion of fetal cells in maternal blood as well as that of maternal cells in UCB was also determined. Material and Methods Three milliliters of peripheral blood was collected from nine women during labor. Five women delivered males and four delivered females. Immediately after delivery, 3 mL UCB was collected. Ten microliters was used to quantitate apoptosis by the ethidium bromide assay (EthBr) and from the remaining blood, Annexin V positive cells were isolated by MACS. Results The Median apoptosis rate in maternal samples was 25% (19–34) and in UCB 20% (16–28). Annexin V positive cells were present in all samples analyzed. As shown by Fluorescence in situ hybridization (FISH) in maternal samples, cells with an XY hybridization pattern were identified in cases with male newborns in a median concentration of 1.7% (1.6–2.1). On the corresponding UCB, a median of 1.2% (0.8‐1.6) XX cells were detected. Conclusion The study demonstrates the existence of a bidirectional transfer of fetal and maternal cells under apoptosis across the placenta and provides useful information regarding use of UCB for transplantation. Copyright © 2007 John Wiley & Sons, Ltd.