THE USE OF POLYMERASE CHAIN-REACTION TO DETERMINE FETAL RHD STATUS

OBJECTIVE: Our purpose was (1) to establish the accuracy of a deoxyrib onucleic acid amplification method in determination of RhD status in a dult blood samples, including weak D variants (previously referred to as D-u) and a D mosaic, and (2) to apply the method to determine fetal RhD status in alloimmunized pregnancies. STUDY DESIGN: Twenty-five ad ult blood samples, including five weak D variants and one D mosaic, we re analyzed with a polymerase chain reaction to determine RhD type. Th e method was then applied to amniotic fluid samples obtained by amnioc entesis from three RhD-negative women with known RhD sensitization. RE SULTS: RhD type determined by polymerase chain reaction for all adult blood samples agreed with serologic typing results. All weak D variant s and the D mosaic gave results consistent with RhD positivity. Fetal RhD status was determined in each of the three alloimmunized pregnanci es, and obstetric management decisions were made on the basis of these results. CONCLUSIONS: This polymerase chain reaction method allows ra pid and accurate determinations of fetal RhD status by amniocentesis. Fetal blood sampling or serial amniocenteses may be avoided when the f etus is RhD negative, and plans for surveillance and intervention can be confidently made if the fetus is RhD positive. However, before the widespread use of this assay, its sensitivity and specificity must be established. Because weak D variants and a D mosaic demonstrated RhD-p ositive status by polymerase chain reaction, the method described is a pplicable to these RhD variants.