Presence of Fetal RNA in Maternal Plasma

The discovery of fetal DNA in maternal plasma (1) has opened up a new horizon on prenatal molecular diagnosis. Many groups have since shown that fetal genetic traits, such as RhD status and inherited genetic diseases, can be determined from fetal DNA in maternal plasma (2)(3)(4)(5). However, it is not known whether fetal RNA is also present in maternal plasma. Here, using a two-step reverse transcription (RT)-PCR assay, we demonstrate the presence of fetal-derived, male-specific mRNA in plasma of pregnant women carrying male fetuses. Pregnant women attending the Prenatal Diagnosis Unit at the Department of Obstetrics and Gynecology, Prince of Wales Hospital, Hong Kong were recruited with informed consent. The study was approved by the Clinical Research Ethics Committee. Women early and late in their pregnancies (n = 21 and 37, respectively) were recruited in this study. The mean gestational ages of the subjects in early and late pregnancies were 16 weeks (range, 11–19 weeks) and 33 weeks (range, 26–40 weeks), respectively. All early-pregnancy samples were obtained before any invasive procedure. On the other hand, late-pregnancy samples were collected either from women who had invasive procedures in early pregnancy (n = 21) or from women who did not have any prenatal invasive procedure (n = 16). All plasma samples were harvested within 30 min from EDTA-blood samples as described previously (1). Total RNA from plasma samples was isolated with the Trizol LS Reagent (Life Technologies) as instructed …