OBJECTIVE: To explore the value of next-generation sequencing for the 
non-invasive prenatal testing of fetal chromosomal aneuploidies.
METHODS: Plasma from 4004 women with singleton pregnancy at a gestational age 
between 12-35(+5) weeks was collected prior to amniocentesis between April 19th 
2011 and December 31st 2013. The samples were divided into three groups: (1) 
High risk for Down syndrome by biochemical screening; (2) Advanced maternal age; 
(3) Abnormalities by ultrasound or other methods. Plasma DNA extracted from 
above samples was sequenced at low coverage. Positive results were verified 
against the karyotypes of the fetuses. For those with negative results, the 
fetuses were followed up by telephone call for at least six months after birth.
RESULTS: Among 4003 samples subjected to non-invasive prenatal diagnosis, 66 
(1.65%) had a positive result. In group 1, 22 cases of trisomy 21 (T21), 3 cases 
of trisomy 18 (T18), 1 case of 13 trisomy (T13), 8 cases of 45,X and 2 cases of 
other chromosomal abnormality were detected. In group 2, 13 cases of T21, 2 
cases of T18, 1 case of T13, 5 cases of 45,X, 2 cases of 47,XXN and 1 case of 
other chromosomal abnormality were detected. In group 3, 1 case of T21, 1 case 
of T18, 1 case of T13, and 3 cases of 47,XXN were detected. For 55 samples 
underwent prenatal diagnosis, 30 cases of T21 and 4 cases of T18 were 
discovered, which was consistent with the results of non-invasive prenatal 
diagnosis. For the 13 cases indicated as 45,X, 3 were verified by karyotype 
analysis, 2 were verified as mosaicism (45,X/46,XN), 8 were 46,XN (false 
positives). For the 5 cases indicated as 47,XXN, 2 were verified by karyotype 
analysis, the other 3 were 46,XN (false positives). Karyotypes of 3 cases 
suspected for other chromosomal abnormalities were all verified as 46,XN (false 
positive). Until May 1st 2014, telephone follow-up for those with negative 
screening results only identified a boy with facial abnormalities and 
developmental delay, which was similar to his older sister, combined karyotyping 
and fluorescence in situ hybridization analysis has verified the karyotype of 
the boy as 46,XY,rec(14)dup(14q)inv(14)(p12q14)pat.
CONCLUSION: Our results indicated that sequencing of plasma free DNA can rapidly 
detect fetal chromosomal aneuploidies. The method is non-invasive, and the 
results are highly consistent with karyotype analysis in terms of accuracy and 
specificity. Non-invasive testing can be used as an effective adjunct to 
conventional prenatal diagnostic methods, which can greatly reduce unnecessary 
invasive prenatal diagnosis. However, the sensitivity and accuracy for 
aneuploidy detection other than chromosome 13/18/21 still need to be improved.