FETAL CELLS IN MATERNAL BLOOD - DETERMINATION OF PURITY AND YIELD BY QUANTITATIVE POLYMERASE CHAIN-REACTION

OBJECTIVE: The detection of fetal aneuploidy and gene mutations by ana lysis of fetal cells in maternal blood has demonstrated the feasibilit y of noninvasive prenatal diagnosis. Fetal cells are rare in the mater nal circulation; all current methods used for their isolation also yie ld maternal cells. We developed a method that permits a quantitative a ssessment of the relative numbers of fetal and maternal cells. STUDY D ESIGN: Samples from 40 pregnant women were flow sorted with different monoclonal antibodies. Deoxyribonucleic acid was subsequently purified from candidate fetal cells; polymerase chain reaction was performed w ith synthetic primers specific for sequences on chromosomes Y and 7. R ESULTS: The maximum number of fetal cells detected was 52 in 1080 mate rnal cells. Fetal cell purity ranged from 0.001% to 4.8%. Fetal cells were detected with antibodies to CD71, CD36, and glycophorin A. CONCLU SION: Quantitative polymerase chain reaction enables the determination of the purity and yield of fetal cells remaining after isolation from maternal blood, facilitating rapid comparisons between different cell separation techniques.