Circulating erythroblasts in maternal blood are not elevated before onset of preterm labor

OBJECTIVE: Preterm labor has recently been reported to be associated with an increased release of cell free fetal deoxyribonucleic acid (DNA) into the maternal circulation. We have previously observed increases in both fetal cell traffic and cell free fetal DNA in preeclamptic pregnancies. In this study, we investigated whether fetal cell traffic is also disturbed in pregnancies with preterm labor. METHODS: In a case-control study, we examined 47 pregnancies complicated by preterm contractions that occurred between 20 and 34 weeks' gestation and an equal number of matched controls. Erythroblasts were enriched for by magnetic cell sorting and enumerated. These values were then correlated with subsequent pregnancy outcome. RESULTS: In the study group 16 patients delivered prematurely (subgroup A). The other 31 (subgroup B) delivered at term, as did all those in the control group. No significant difference was noted in erythroblast numbers between either one of the subgroups and die controls. CONCLUSION: Contrary to the reported increased levels of free fetal DNA in maternal serum, erythroblasts in maternal blood are not elevated significantly in pregnancies with threatened premature labor or in those that deliver preterm.