In this study we have investigated whether quantitative analysis of placental mRNAs in maternal plasma provides a way to monitor placental status. We measured plasma concentrations of human chorionic gonadotropin beta-subunit (betahCG) and human placental lactogen (hPL) mRNAs as previously reported mRNAs and pregnancy associated plasma protein A (PAPP-A), placenta-specific 1 (PLAC1) and glial cells-missing 1 (GCM1) mRNAs, which have not been measured during the course of normal pregnancy. Firstly, peripheral blood was obtained at various times from healthy pregnant women to clarify the time course of placental mRNAs. Secondly, blood was obtained from women with pre-eclampsia and gestational age-matched controls to examine whether placental mRNAs change in pre-eclampsia. Plasma was separated from these samples for extraction of RNA, followed by reverse transcription polymerse chain reaction analysis. Median concentrations of PLAC1 and GCM1 mRNA in plasma of pre-eclamptic subjects respectively were 1625 and 2141 copies/ml, significantly higher than 195 and 881 copies/ml, the values for controls (Mann-Whitney test, p<0.001). No significant difference was seen in hPL, betahCG, or PAPP-A mRNA concentration between pre-eclamptic and control groups. Plasma PLAC1 and GCM1 mRNAs appear promising as noninvasively measurable molecular markers for pre-eclampsia.