Increased fetal erythroblasts in women who subsequently develop pre-eclampsia

In pregnancies complicated by pre-eclampsia (PET) and/or intrauterine growth restriction (IUGR) there is an increased number of fetal cells in the maternal circulation. The aim of this study was to investigate whether this increase in fetal cells precedes the onset of these pregnancy complications. Doppler ultrasound studies at 24 weeks gestation have shown that increased impedance to flow in the uterine arteries identifies pregnancies with impaired placental perfusion that subsequently develop PET and/or IUGR. We obtained maternal blood from 18 pregnancies with abnormal Doppler results at 22-24 weeks gestation and from 10 normal controls. Fetal erythroblasts were enriched from maternal blood by triple density gradient centrifugation and magnetic cell sorting with CD71 antibody, and the percentage of these erythroblasts was determined. The median proportion of fetal erythroblasts in the group with abnormal Doppler results was 4.5% (range 1-12%), which was significantly higher than in the control group [median 1% (range 0-3%; P < 0.001)]. Furthermore, within the group with abnormal Doppler the median proportion of fetal erythroblasts was higher in the 10 cases which subsequently developed PET and/or IUGR [median 5.5% (range 3-12%)], than in those with normal pregnancy outcome [median 2% (range 1-5%; P < 0.01)]. These findings suggest that impaired placental perfusion is associated with an increase in feto-maternal cell traffic, which precedes the onset of PET and/or IUGR by several weeks.