Abstract
<title>Abstract</title> <p>Genome-wide SNP-array genotyping of maternal plasma cell-free-DNA (cfDNA) could extend applications of non-invasive prenatal testing, but low cfDNA quantity may limit performance. This study evaluated minimum amounts of genomic-DNA (gDNA) and cfDNA required for successful genotyping during pregnancy. Thirty healthy pregnant women from the Newcastle 1000 Study were recruited. gDNA and cfDNA were genotyped using the Illumina Global Screening Array with DNA inputs ranging from 20 to 200ng. Genotyping success was defined as SNP-array call rate (CR) ≥ 95%, and concordance analyses assessed reproducibility. All gDNA experiments (n = 83) successfully genotyped, including those using 20ng DNA (mean CR 99.16%). Of 48 cfDNA experiments, 81.3% successfully genotyped. All 50ng cfDNA samples successfully genotyped (mean CR 96.88%). Concordance were 100.00% for gDNA and 99.89% for cfDNA. Accurate, reproducible SNP-array genotyping is feasible with as little as 10% of the recommended DNA amount, but further discussion on clinical implications is needed to demonstrate real-world utility.</p>