Volume 1022, Issue 1 p. 119-123

A Clinical Service in the UK to Predict Fetal Rh (Rhesus) D Blood Group Using Free Fetal DNA in Maternal Plasma

KIRSTIN FINNING

Corresponding Author

KIRSTIN FINNING

International Blood Group Reference Laboratory, National Blood Service, Bristol BS10 5ND, UK

Address for correspondence: Kirstin Finning, International Blood Group Reference Laboratory, National Blood Service, Southmead Road, Bristol BS10 5ND, UK. [email protected]Search for more papers by this author
PETER MARTIN

PETER MARTIN

International Blood Group Reference Laboratory, National Blood Service, Bristol BS10 5ND, UK

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GEOFF DANIELS

GEOFF DANIELS

International Blood Group Reference Laboratory, National Blood Service, Bristol BS10 5ND, UK

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First published: 08 July 2009
Citations: 105

Abstract

Abstract: Antenatal determination of fetal blood group is important in pregnancies with a significant risk of hemolytic anemia due to maternal alloimmunization. The International Blood Group Reference Laboratory (part of the National Blood Service) in Bristol, UK, provides a fetal blood group genotyping service to obstetricians caring for immunized pregnant women with heterozygous partners. Since 2001, fetal D typing has been offered using free fetal DNA in maternal plasma. Real-time polymerase chain reaction (PCR) assays are performed to detect the RHD gene. To confirm the presence of fetal DNA when RHD is not detected, Y-chromosome sequences are targeted. When a D-negative female fetus is predicted, maternal buffy coat DNA is tested for eight insertion/deletion polymorphisms. Sequences that are absent from the maternal genome are then targeted in maternal plasma and are used to confirm the presence of free fetal DNA in the blood sample. Currently, 283 pregnancies have been tested, of which 50 are awaiting confirmatory results. Fetal D status was correctly predicted in 223 cases, and no result was obtainable in 7 cases. In three cases, serology on cord blood was discrepant with reported results, but all fetuses had received multiple intrauterine transfusions. The new test has significantly reduced the number of invasive procedures carried out in the UK for fetal D grouping. Antenatal anti-D prophylaxis is currently being introduced in the UK to all D-negative women; in the future, detection of fetal RHD sequences in maternal plasma may allow anti-D to be restricted to pregnancies involving a D-positive fetus.