Stepwise molecular-genetic examination in aborted fetuses

Objective: The evaluation of quantitative fluorescence PCR (QF-PCR) and single nucleotide polymorphism array (SNP array) analysis for the identification of chromosomal abnormalities in products of conception (POC). Materials and methods: A total of 1,094 POC samples were processed at Gennet in the years 2018-2020. Chromosomal aneuploidies were tested by QF-PCR using a Omnibor set (STR markers 13, 18, 21, X a Y), SAB-I set (STR markers 2, 7, 15, 16, 22), SAB-II set (from November 2019, STR markers 4, 6, 14) followed by SNP array analysis (Illumina) on samples with a negative QF-PCR result. All POC samples were tested for maternal contamination. Results: After exclusion of maternal contamination (32% samples) the total number of 742 POC samples were tested by QF-PCR. Chromosomal aneuploidies were found in 273 POC samples (36.8%). Then, 469 QF-PCR negative POC samples were tested by SNP array analysis. Normal female/male profile was confirmed in 402 samples (85.7%) and chromosomal aneuploidies and chromosomal aberrations (deletion/duplication > 10 Mb) in 51 samples (10.9%). Microdeletion/microduplication was found in 16 POC samples (3.4%), two were classified as pathogenic variants and 14 as variants of unknown significance. In a group of women > 35 years of age, statistically significant increase of the chromosomal abnormalities was confirmed. No statistically significant difference between the in vitro fertilization group and the group of spontaneous conception was found. Conclusion: The application of the molecular work-up based on the stepwise use of QF-PCR and SNP array clarifies the cause of the abortion in 43% POC samples. The overall detection rate in the I. trimester was 50.4%.