Background: Increased fetal DNA in maternal plasma/serum has been reported in pregnancies complicated by preeclampsia. We hypothesize that fetal RNA may also be increased in maternal plasma in preeclampsia.

Methods: We developed a real-time quantitative reverse transcription-PCR assay to measure the concentration of the mRNA of the corticotropin-releasing hormone (CRH) locus. Peripheral blood samples were obtained from healthy pregnant women both before and 2 h after delivery. Peripheral blood samples were also obtained from women suffering from preeclampsia and controls matched for gestational age. Plasma was harvested from these samples, and RNA was extracted. Plasma RNA was subjected to analysis by the reverse transcription-PCR assay.

Results: CRH mRNA was detected in the plasma of 10 healthy pregnant women in the third trimester. CRH mRNA was found to be cleared very rapidly after cesarean section, with no detectable signal by 2 h postpartum. Plasma CRH mRNA concentrations were 1070 and 102 copies/mL, respectively, in 12 preeclamptic women and 10 healthy pregnant women matched for gestational age (Mann–Whitney test, P <0.001).

Conclusion: Plasma CRH mRNA represents a new molecular marker for preeclampsia. Maternal plasma RNA is gender- and polymorphism-independent and may allow noninvasive gene-expression profiling of an unborn fetus.