shiura,2 and Hideaki Masuzaki1 Departments of 1 Obstetrics and Gynecology and

have been identified as pregnancy-associated mole-cules with the potential for use in estimating the con-dition of the placenta. Our understanding of these novel molecules is still limited, however. The aim of this study was to isolate and characterize pregnancy-associated miRNAs in maternal plasma. METHODS: By microarray-based screening of 723 hu-man miRNAs, we selected miRNAs that exhibited signal intensities 100 times higher in placental tissues than in the corresponding whole blood sam-ples. Subsequent quantitative real-time reverse-transcription PCR revealed miRNAs produced predominantly in the placenta that showed signifi-cantly decreased concentrations in maternal plasma after delivery. These miRNAs were identified a