Detection Of Fetal DNA In Maternal Plasma And Its Clinical Application In Noninvasive Prenatal Diagnosis

OBJECTIVE:To detect free fetal DNA in maternal plasma,explore the possibility of prenatal gene diagnosis for fetal sex determination-with free fetal DNA and search a new method of non-invasive prenatal gene diagnosis.METHODS:Cell-free fetal DNA was extracted by column extraction seperation from 34 pregnant women plasma(between 17～18week)and 12 pregnant women plasma(between 29～40week),nested polymerase chain reaction was employed to amplify the SRY gene of Y chromosome,and ATL1 gene specific sequence of FMR1 gene on X chromosome was amplified as an internal control by semi- nested polymerase chain reaction.RESULTS:The SRY sequence was detected in 26 plasma samples obtained from 28 pregnant women carring male fetuses.In 17 cases of 18 pregnancies with female fetuses,only the ATL1 gene sequence was detected,and SRY gene was detected in 1 case.The sensitivity rate was 92.9%(26/28),the specific rate was 94.4%(17/18),and the accurate rate of this method was 93.5%(43/46)CONCLUSIONS:Free fetal DNA in maternal plasma can be used for prenatal diagnosis of fetal sex determination incompetibility;The nested PCR that detects free fetal DNA in maternal plasma possesses the advantages of sensitivity,specificity and accurate rate.It can be used for clinic as a non-invasive prenatal gene diagnostic method.