Abstract
BackgroundThis study was an evaluation of the role of noninvasive prenatal testing (NIPT) in the detection of trisomy 7 in prenatal diagnosis.MethodA total of 35 consecutive cases underwent screening for trisomies by cell-free DNA testing between April 2015 and November 2017 due to suspicious NIPT results; these cases represented 0.11% of patients (35/31,250) with similar frequencies of abnormal results among the laboratories performing the tests. NIPT was offered to further screen for common fetal chromosomal abnormalities. Karyotype analysis, chromosomal microarray analysis (CMA), and next-generation sequencing (NGS) were used to detect 20, 14, and 25 patients, respectively, who accepted confirmatory diagnostic testing.ResultsHigh-risk results by NIPT were recorded for trisomy 7 alone in 29 women: dual aneuploidy in 4 patients and multiple aneuploidy in 2 patients. Karyotype analysis of amniotic fluid cells was normal in all 20 pregnancies, suggesting a probability of confined placental mosaicism. Further CMA data were obtained in 14 of the cases mentioned above, and 2 fetuses were detected with positive results with copy number variation. The NGS results suggested that all these samples were placental chimerisms of chromosome 7, except for one sample that was found to be an additional chimerism of chromosome 2, which was also consistent with the NIPT result.ConclusionOur results may be useful for the counseling of pregnant women in the detection of trisomy 7 by NIPT.
Highlights
This study was an evaluation of the role of noninvasive prenatal testing (NIPT) in the detection of trisomy 7 in prenatal diagnosis
The next-generation sequencing (NGS) results suggested that all these samples were placental chimerisms of chromosome 7, except for one sample that was found to be an additional chimerism of chromosome 2, which was consistent with the NIPT result
Our results may be useful for the counseling of pregnant women in the detection of trisomy 7 by NIPT
Summary
This study was an evaluation of the role of noninvasive prenatal testing (NIPT) in the detection of trisomy 7 in prenatal diagnosis. In the latest meta-analysis, the pooled sensitivity was 99.4% for trisomy 21, 97.7% for trisomy 18, and 90.6% for trisomy 13 [1] The specificity for these aneuploidies was 99.9% to 100% [2]. In a large cohort study performed recently, NIPT data were generated from 89,817 unique pregnancies, showing that single rare autosomal trisomies (RATs) were the most frequently observed chromosome abnormalities and accounted for 0.34% of the total sample [6]. The frequency of trisomy 7, which is the most commonly reported RAT in both the NIPT and chorionic villi sampling (CVS) data sets, was comparable at 0.0746% and 0.0795%, respectively [7]
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