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To determine the detection rate of clinically significant chromosome abnormalities using quantitative fluorescent polymerase chain reaction (QF-PCR) of fetal DNA in comparison with G-banded analysis of cultured amniotic fluid cells and determine the residual risk if QF-PCR were performed alone for low-risk cases.Amniotic fluid samples were prospectively categorized based on the likelihood of the fetus having a chromosome anomaly. QF-PCR results were compared with the G-banded findings. The distribution of patients and the rates of clinically significant anomalies in each risk category were determined.A total of 4176 amniotic fluid samples were studied. Among these, 331 cases with abnormalities were detected by both methods and an additional 19 abnormal cases were detected by G-banding only. Five of those undetected by QF-PCR were considered clinically significant, four of which were referred due to an elevated a priori risk (>4%). If QF-PCR is performed in all cases and G-banding performed only in higher risk cases, the residual risk for a clinically significant chromosome abnormality will be as low as 0.083%.This study suggests that QF-PCR alone is appropriate for patients with uncomplicated pregnancies, who are referred solely for an increased risk of a common trisomy. Copyright © 2011 John Wiley & Sons, Ltd.