Placental RNA in maternal plasma: toward noninvasive fetal gene expression profiling

The recent demonstration of the presence of placenta-derived fetal RNA in maternal plasma has opened up new opportunities for noninvasive prenatal investigation. Circulating fetal RNA analysis could in principle be applied to all pregnancies without the limitations by fetal gender or polymorphisms between the mother and fetus. The use of fetus- or disease-specific circulating RNA markers would greatly increase the number of markers that can be used for prenatal monitoring. With the recent advances in microarray technology, new placenta-derived plasma RNA markers could be rapidly identified. These newly identified placental transcripts were robustly detectable in maternal plasma and were pregnancy-specific. Remarkably, the relative concentrations of the placental mRNA in maternal plasma directly reflect the gene expression patterns in the placenta, an observation which suggests that placental gene expression level plays a predominant role in determining the placental mRNA concentrations in maternal plasma. Thus, fetal mRNA measurement in maternal plasma may be a useful tool for noninvasive prenatal placental gene expressing profiling.