To set up a semi‐quantitative microarray method for the detection of fetal RNAs in maternal plasma.

We developed a semi‐quantitative microarray method for the detection of placental RNA in maternal plasma. Firstly, the selected fetal RNAs were linearly amplified from the maternal plasma and then fluorescently labeled as the target DNAs. Finally, the targets were hybridized and detected by capturing DNA probes on a microarray slide. Two genes of beta subunit of human chorionic gonadotrophin (β‐hCG) and zinc finger gene on the Y chromosome (ZFY) were assayed with the microarray, and beta actin gene was used as an internal standard. Eighty‐five pregnant women in the first trimester and the third trimester of gestation joined in this experiment, 14 of them also sampling in 36 h after delivery for the same assay. Real‐time quantitative PCR was performed for comparison.

It was found that the mRNA level of β‐hCG decreased with the increasing of gestation age, and it was much higher in the carriers of the female fetus than in the carriers of the male fetus in the first trimester of gestation, which was consistent with the real‐time quantitative PCR results. The results also reveal that delivery would result in the clearance of fetal mRNA in maternal plasma.

The results suggest that the semi‐quantitative microarray method has great potential as a high‐throughput assay in prenatal diagnosis and clinical laboratory. Copyright © 2005 John Wiley & Sons, Ltd.