Evaluation of Human Chorionic Gonadotropin β-Subunit mRNA Concentrations in Maternal Serum in Aneuploid Pregnancies: A Feasibility Study

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Abstract
The recent demonstration of detectable circulating fetal RNA in maternal plasma (1)(2) has led to the development of new, noninvasive prenatal diagnostic opportunities (3)(4). Unlike fetal DNA measurements in maternal plasma/serum, quantitative analysis of circulating fetal RNA has the advantage of being applicable to all pregnant women irrespective of fetal gender and genetic polymorphism status. In addition, the unexpected stability of circulating RNA has enhanced the practicality of this approach (2)(5)(6). Previously, we developed a real-time quantitative reverse transcription-PCR (RT-PCR) assay for measuring the concentration of human chorionic gonadotropin β-subunit (β hCG ) mRNA in plasma samples from healthy pregnant women (2). We conducted a case–control study to investigate whether abnormal concentrations of β hCG mRNA might be detectable in the serum of mothers carrying fetuses with trisomy 21 and trisomy 18. We sought informed consent from pregnant women who presented for aneuploidy screening at the King’s College Hospital London in the United Kingdom between January and August 2003. Ethics approval was obtained from the Institutional Review Board. Among women who underwent chorionic villous sampling for fetal karyotyping as a result of clinical indications, 149 women consented to blood sampling for β hCG mRNA measurements. Maternal blood samples were collected into plain tubes immediately before chorionic villous sampling. The blood samples were centrifuged at 1600 g for 10 min at 4 °C. The serum was carefully transferred into plain polypropylene tubes, and 3.2 mL was immediately stored in 4 mL of Trizol and kept at −80 °C until RNA extraction. Serum RNA was extracted from 1.6 mL …