[Clinical significance of secondary results from non-invasive prenatal testing]

To assess the accuracy of copy number variations (CNVs) detection by non-invasive prenatal testing (NIPT) in addition to its routine targets and clinical significance of such CNVs for the reduction of fetuses born with chromosomal microdeletion/duplication syndromes.

From October 2014 to October 2015, 14 235 pregnant women volunteered to participate in the study. Fifteen cases detected with chromosomal CNVs by the NIPT decided to undergo prenatal diagnostic procedures including amniocentesis, G-banded karyotyping and chromosomal microarray analysis (CMA). All such cases were routinely followed up after birth.

Among the 14 235 subjects underwent NIPT, 18 cases were detected with Down syndrome, 4 with trisomy 18, and 2 with trisomy 13, in addition with 24 cases of CNVs. For the latter, 15 (including 11 cases with microdeletions and 4 cases with microduplications) participated in further prenatal diagnosis. In 13 cases (86.7%), the results of CMA were consistent with those of NIPT. On the other hand, only 7 out of the 15 cases showed a positive result with karyotyping, suggesting a rather high rate of missed diagnosis (46.2%). Of note, karyotyping has identified partial inversion of chromosome 9 in one case.

As a screening tool, NIPT has a high accuracy for the detection of CNVs. However, as this method is still under improvement, it is more of a reminder rather than a diagnostic tool with full capability.