Abstract: Objective　To investigate the feasibility of free fetal DNA from maternal plasma in noninvasive prenatal diagnosis. Methods　Free fetal DNA was extracted by column seperation from 46 maternal plasma， and nested polymerase chain reaction (PCR) was used to amplify the SRY gene， and ATL1 gene specific sequence was amplified as an internal control. Results　The SRY gene sequence was detected in 26 maternal plasmas from 28 pregnant women with male fetus. In 17 maternal plasmas from 18 pregnant women with female fetus， only the ATL1 gene sequence was detected. The sensitivity was 92.9％（26/28），the specificity was 94.4%（17/18）， and the coincidence rate was 93.5％（43/46）. Conclusions　Free fetal DNA from maternal plasma analysis is a noninvasive prenatal diagnosis and has the advantages of sensitivity and specificity， and it can improve in the clinical application.

Key words: Fetal DNA, Nested polymerase chain reaction, Prenatal diagnosis