• Ranjit Akolekar, Kirstin Finning, Ramesh Kuppusamy, Geoff Daniels, and Kypros H Nicolaides.
• Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London, UK.
• Fetal. Diagn. Ther. 2011 Jan 1;29(4):301-6.

ObjectiveTo examine the feasibility of fetal RHD genotyping at 11-13 weeks' gestation from analysis of circulating cell-free fetal DNA (ccffDNA) in the plasma of RhD negative pregnant women using a high-throughput robotic technique.MethodsStored plasma (0.5 ml) from 591 RhD negative women was used for extraction of ccffDNA by a robotic technique. Real-time quantitative polymerase chain reaction (PCR) with probes for exons 5 and 7 of the RHD gene was then used to determine the fetal RHD genotype, which was compared to the neonatal RhD phenotype.ResultsIn total there were 502 (85.7%) cases with a conclusive result and 84 (14.3%) with an inconclusive result. The prenatal test predicted that the fetus was RhD positive in 332 cases and in all of these the prediction was correct, giving a positive predictive value of 100% (95% CI 96.8-100). The test predicted that the fetus was RhD negative in 170 cases and in 164 of these the prediction was correct, giving a negative predictive value for RhD positive fetuses of 96.5% (95% CI 93.7-99.2).ConclusionThe findings demonstrate the feasibility and accuracy of non-invasive fetal RHD genotyping at 11-13 weeks with a high-throughput technique.Copyright © 2011 S. Karger AG, Basel.

14 keywords...

hide…