OBJECTIVETo analyze cell-free fetal DNA in maternal plasma for prenatal screening of beta-thalassaemia major.

METHODSSix couples undergoing prenatal diagnosis of beta-thalassaemia (gestational age range 23-26 weeks) were enrolled in this study. The husbands were all carriers of the CD17 (A-->T) mutation, and the wives carried another beta-thalassaemia mutation. The allele-specific primers and two fluorescent cycling probes were synthesized for the detection of the CD17 (A-->T) mutation, using FAM and HEX fluorescence labeling, respectively. The cell-free fetal DNA in the maternal plasma was detected using real-time PCR, and the fetal genotype was confirmed by cord blood conventional prenatal diagnosis.

RESULTSIn the 6 pregnancies, FAM and HEX fluorescent signals were detected in 3 maternal plasma samples; in the other 3 samples, only FAM fluorescent signals were detected, suggesting the absence of paternally derived CD17 (A-->T) mutation.

CONCLUSIONExamination of cell-free fetal DNA in maternal plasma using real-time PCR and cycling probe technology can be effective means for prenatal screening of beta-thalassaemia major.