Background: Analysis of fetal DNA from maternal

plasma by PCR offers great potential for noninvasive prenatal genetic diagnosis. To further evaluate this potential, we developed and validated a standard pro-tocol to determine whether fetal DNA sequences could be reproducibly amplified and measured across multi-ple laboratories in a common set of specimens. Methods: Each of five participating centers in a Na-tional Institute of Child Health and Human Develop-ment consortium collected 20 mL of peripheral blood from 20 pregnant women between 10 and 20 weeks of gestation. The plasma fraction was separated according to a common protocol, divided, and frozen in five aliquots. One aliquot was shipped to each participating laboratory, where DNA was extracted according to a standard protocol. All plasma samples (n 100) wer