NON-INVASIVE CELL FREE FETAL RHESUS D (RHD) GENOTYPING

Non-Invasive Cell Free Fetal Rhesus D (RHD) Genotyping

Non-invasive cell free fetal Rhesus D testing is now available to enable targeting of antenatal anti-D prophylaxis for Rhesus D (RHD) negative pregnant women that are carrying an RHD positive baby. Only RHD negative mothers carrying an RHD positive baby have a risk of developing antibodies that could affect future pregnancies if they do not receive anti-D prophylaxis.  The RHD negative pregnant mothers that are shown to be carrying an RHD negative baby will not require prophylactic anti-D treatment.

Analysis involves amplification and detection of the fetal RHD genotype in a mixture of maternal and fetal cell free DNA using a sensitive Taqman® Genotyping assay (Finning et al 2008).  The test methodology does not measure fetal fraction which means that there is a very small possibility of a false negative result due to low fetal DNA (False RhD negative % (CI) 0.10 (0.02 to 0.59) (Chitty et al 2014 BMJ 4:349)). Uncertainty of measurement for the assay is available upon application to the laboratory

Testing within the Royal Devon & Exeter Hospital is provided as part of the routine first trimester screening service. Please see link for sample requirements for internal and external requests. 

Queries regarding testing should be directed to:

Dr Jayne Houghton (Clinical Scientist on 01392-408244 or jaynehoughton@nhs.net) or Rde-tr.MolecularGeneticsAdmin@nhs.net