P-387 The use of cell-free DNA analysis to identify fetal aneuploidies in early pregnancy loss

Abstract

Abstract Study question Can cell-free (cf) DNA-based analysis of a maternal blood sample be used to identify presence of fetal aneuploidies in early pregnancy loss (EPL) cases? Summary answer CfDNA analysis was able to detect fetal aneuploidies in EPL cases with 73.5% sensitivity and 100% specificity. What is known already Miscarriages occur in about 10%–20% of pregnancies, and the majority occur in the first trimester. About 50% of EPL cases result from the presence of fetal aneuploidy. Knowing the etiology of a miscarriage can be helpful for future reproductive planning along with providing a psychological benefit for patients. Although products of conception (POC) samples can be collected and assessed for presence of fetal aneuploidies, this is not always possible. Recent studies have shown that a noninvasive approach using cfDNA analysis of a blood sample can identify fetal aneuploidies in patients that experience EPL. Study design, size, duration In this prospective study, samples were collected from 78 patients across the United States from June 2021–December 2022. Blood specimens were collected for cfDNA analysis and maternal cell contamination analysis, and POC samples were collected following surgical evacuation for microarray analysis. Performance of the cfDNA assay was determined by comparing results from the cfDNA analysis against the gold standard of microarray results. Participants/materials, setting, methods Patients were recruited from six reproductive endocrinology/infertility practices. Eligible participants were between 5–20 weeks of gestation with miscarriage of a singleton pregnancy diagnosed by ultrasound and presence of pregnancy tissue in utero. Limited clinical information was collected, including demographics and expected clinical gestational age (GA) at sample collection. Blood samples underwent cfDNA analysis using an adapted version of a noninvasive prenatal test, which included establishment and use of pregnancy loss-specific log likelihood ratio thresholds. Main results and the role of chance Seventy-eight patients were recruited, of which two were excluded due to blood sample collection issues. Eleven of the 76 patients that underwent cfDNA analysis were excluded from performance calculations for several reasons including maternal cell contamination of POC samples and detection of triploidy by microarray. The final 65 samples included 49 affected and 16 unaffected samples based on POC microarray results; this included 42 with one fetal aneuploidy, six with two fetal aneuploidies, and one with three fetal aneuploidies. Average fetal fraction of these 65 samples was 4.9% (range: 0.6%–13.9%) and average expected clinical GA at time of sample collection was 8.7 weeks (range: 5.9–12.1 weeks). Performance of the cfDNA assay was determined by comparing cfDNA analysis results with POC microarray results using either a full concordance approach (correct classification of all affected chromosomes in an affected sample) or a partial concordance approach (correct classification of at least one affected chromosome in an affected sample). Based on the full concordance approach, sensitivity of the cfDNA assay was 69.4% and specificity was 100%. For the partial concordance approach, sensitivity of the cfDNA assay increased to 73.5% whilst specificity remained at 100%. The cfDNA assay failure rate was 0%. Limitations, reasons for caution Study limitations include a small study cohort, the inability of the cfDNA assay to detect triploidy or partial deletions/duplications <7 Mb and possibly mosaicism, and that this cfDNA analysis approach can only be used for EPL cases that are identified before complete expulsion of the products of conception. Wider implications of the findings This study provides further evidence of the ability of cfDNA analysis to detect fetal aneuploidies in EPL cases. A clinically available cost-effective noninvasive approach to determine the etiology of a miscarriage could help inform medical management of patients for future reproductive planning and could provide psychological benefits to patients. Trial registration number NCT04935138