Uniparental disomy, polyploidy, and low percentage chimeras can also be detected using these techniques 4, 5, 6, 7. These arrays facilitate high resolution, high-throughput whole genome screening and SNP-array detection of CNVs that cannot be detected by karyotype analysis, including chromosomal microdeletion or microduplication. Single nucleotide polymorphism array (SNP-array) is one of the many techniques used in chromosome microarray analysis (CMA). However, karyotype analysis cannot identify copy number variations (CNVs) of less than 10 Mb 2, requires technical expertise and is subject to a long detection cycle 3. Currently, the criteria to perform invasive prenatal diagnostic tests are (1) non-invasive prenatal testing (NIPT)-positive results (2) abnormal ultrasound structures (3) chromosomal abnormalities in couples (4) high-risk STSS results (5) advanced maternal age (≥ 35 years) (6) ultrasound soft markers and (7) adverse pregnancy history. These methods have served as the gold standard for the diagnosis of fetal abnormalities 1, especially in pregnant women with fetal malformations identified by ultrasound imaging or those with higher risk second trimester serum screening (STSS) results. Methods of chromosome evaluation using amniotic fluid, umbilical cord blood, and chorionic villus sampling have been widely used since the 1970s. There was little correlation between pCNVs and a previous history of adverse pregnancy outcomes, suggesting that genetic screening under these conditions should be evaluated on a case-by-case basis. The different pCNV rates in the three groups were statistically significant.

A total of 3424 fetuses with ultrasonic soft markers were classified as having one, two, or three ultrasonic soft markers. Further evaluation of the 1495 cases with ultrasound abnormalities revealed that the highest pCNV rates were recorded in those cases with multiple system structure abnormalities (22.6%), followed by the groups with skeletal system (11.6%) and urinary system abnormalities (11.2%). Notably the adverse pregnancy history group presented with the lowest pCNVs rate (2.8%). Among the seven different risk factor groups, the non-invasive prenatal testing-positive group had the highest pCNVs rate (35.3%), followed by the abnormal ultrasound structure group (12.8%), and then the chromosomal abnormalities in the couples group (9.5%). Pathogenic copy number variations (pCNVs) were found in 699 (8.3%, 699/8386) cases. Here, SNP-array was used for the retrospective analysis of 8386 pregnancies and the cases were categorized into seven groups. Numerous studies have evaluated the use of single nucleotide polymorphism array (SNP-array) in prenatal diagnostics, but very few have evaluated its application under different risk conditions.

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