ABSTRACT
OBJECTIVE@#To explore the cause for the failure of non-invasive prenatal testing (NIPT) and feasibility of repeated testing.@*METHODS@#Clinical data, test results and pregnancy outcomes of 40 311 pregnant women who received NIPT test from January 2011 to December 2018 were reviewed.@*RESULTS@#Among all the pregnant women, 1116 cases failed in the first test, 9 cases (0.81%) had fetal free DNA concentration lower than 4%, 663 cases (59.41%) were retested after the establishment of Z value gray area, and the remainder 444 cases (39.78%) needed to be retested after the blood collection due to the fetal free DNA concentration lower than 4%. After retesting, 1069 cases (95.78%) obtained effective NIPT results. The results showed that 53 cases were at high risk (6 cases for trisomy 21, 6 cases for trisomy 18, 13 cases for trisomy 13, 16 cases for sex chromosomal abnormality, 12 cases for chromosomal copy number variation). Forty-eight cases were selected for invasive prenatal diagnosis, and 2 cases of 47, XXY and 2 CNV were confirmed. A total of 47 cases (0.12%) did not obtain results because the concentration of fetal free DNA was lower than 4%. Only 16 cases (34%) chose invasive prenatal diagnosis.@*CONCLUSION@#Repeated detection of the gray area of Z value can reduce the false positive rate of NIPT and invasive prenatal diagnosis, and the feasibility of repeated detection is high. In the case of fetal free DNA concentration lower than 4%, the success rate of obtaining effective NIPT results by re-sampling and re-detection increases with the increase of gestational age, but may delay the diagnosis for fetal aneuploidies. Therefore, personalized estimation should be made according to gestational age and clinical indications. It is suggested that pregnant women should choose invasive prenatal diagnosis when they have failed in the retest.
ABSTRACT
<p><b>OBJECTIVE</b>To detect chromosomal imbalance in a fetus with complex congenital heart disease, and to correlate the genotype with the phenotype.</p><p><b>METHODS</b>Routine G-banding was carried out to analyze the karyotypes of the fetus and its parents, and single nucleotide polymorphisms array (SNP-array) was used for delineating fine genomic aberrations. The detected aberrations were confirmed with multiplex ligation-dependent probe amplification (MLPA).</p><p><b>RESULTS</b>The fetus and its parents all showed a normal karyotype, while array-SNP has detected a 13.87 Mb duplication at 4p16.3-p15.33 and a 15.65 Mb deletion at 11q23.3-q25 in the fetus. The results were confirmed by the MLPA assay.</p><p><b>CONCLUSION</b>The partial trisomy 4p (Wolf-Hirschhorn syndrome) and partial monosomy 11q (Jacobsen syndrome) probably underlie the complex heart defects detected in the fetus. Analysis of the karyotypes of its parents offered no help for the determination of the aberrant type and recurrent risk. Compared with routine karyotype analysis, aberrant regions can be identified with array-SNP with greater resolution and accuracy. This has provided useful information for prenatal diagnosis and genetic counseling.</p>