Fetal cells in maternal plasma are found in a late state of apoptosis

The present study was designed to give possible answers to some of the discrepancies regarding the presence or not of intact fetal cells in maternal plasma during pregnancy.

12-mL peripheral blood was collected from 33 pregnant women in the second trimester: 6 mL was harvested by 3-step Percoll gradient centrifugation and plasma cells were analyzed by FISH with X/Y chromosome specific probes. From the remaining 6 mL, plasma-derived cells were isolated with three different gradient centrifugation protocols and apoptosis was determined following EthBr staining.

The number of cells recovered ranged from 900 to 3000. At least one Y positive signal was seen in 12 out of 17 cases with male fetuses at a frequency of 0.12% (range 0.05-0.27%). No XY cells were detected in the plasma of women carrying female fetuses. Hybridization efficiency was <60%. EthBr staining demonstrated that the majority of these cells were in their late apoptosis.

Our findings confirm the presence of intact fetal apoptotic cells in maternal plasma; however, their late apoptotic state and the low number does not as yet encourage their use in clinical practice.