Elevations in fetal cell traffic as well as increased release of cell-free fetal DNA into the maternal periphery have previously been shown to occur in pregnancies affected by preeclampsia. Our own investigations have shown that manifestation of preeclampsia is associated with an increased accumulation of circulatory fetal DNA as well as cell-free maternal DNA in maternal plasma. We further established that the increments in these two molecular genetic analytes corresponded to the severity of the disease and to each other. This latter phenomenon was evident in preeclamptic pregnancies, but not in normal ones. As we had recently performed a prospective study to investigate fetal cell traffic prior to onset of preeclamptic symptoms, we examined the levels of cell-free fetal and maternal DNA in these samples. This analysis indicated that circulatory fetal DNA concentrations were significantly elevated prior to onset of the disease symptoms. No similar feature was observed for cell-free maternal DNA levels.