Factors, pregnancy outcomes, and management associated with non-reportable results in prenatal cell-free DNA testing.

Purpose: To offer more effective strategies by classification of non-reportable results for physicians to manage those pregnancies.

Methods: From July 2022 to May 2024, a total of 14,073 prenatal cell-free DNA (cfDNA) tests were performed by massively parallel sequencing (MPS) in our genetic laboratory and 52 cases received non-reportable results caused by different reasons. Chi-square analysis and logistic regression analysis were used to analyze the risk factors contributing to non-reportable results. The redraw test results and the pregnancy outcomes were collected and analyzed.

Results: Overall, 52 (0.37%) of 14,073 pregnant women had non-reportable cfDNA testing results after the first draw. Multivariate logistic regression analysis revealed that pregnancies conceived by in vitro fertilization (IVF) (OR = 2.42, 95% CI 1.08-5.42, P = 0.03) and heparin use (OR = 7.04, 95% CI 2.40-20.62, P < 0.001) were independent factors for non-reportable cfDNA test results. In 52 cases with non-reportable results, 27 (51.92%) cases had borderline Z scores, 15 (28.85%) cases had a low fetal fraction (< 4.0%), 5 (9.62%) cases indicated multiple chromosomal aberrations (MCA, ≥ 4), and 5 (9.62%) cases had data fluctuation in sex chromosomes. All 52 (100%) cases chose to have a redraw test. The overall success rate of redraw test was 65.38%; however, cases with MCA mainly caused by cfDNA from uterine fibroids or maternal malignancies had relatively low success rate of redraw testing. Compared to pregnant women without risk factors, those with caution indications and with low fetal fraction (LFF) had a lower chance to obtain valid redraw testing results (100.00% vs 16.67%, P = 0.002). The abnormal conditions of perinatal women and infants were more frequent in the cases with non-reportable results after redraw tests (2.94% vs 14.71%, P = 0.027; 7.41% vs 14.81%, P = 0.038).

Conclusion: Repeated testing was not suitable for all cases with non-reportable results. Invasive prenatal diagnosis should be recommended for cases with MCA, cases with caution indications and with low fetal fraction for the first non-reportable results, cases with consecutive non-reportable cfDNA results. More attention should be paid to the cases with non-reportable cfDNA results, especially to the cases with non-reportable redraw testing results.