Prenatal diagnostic testing decisions in twin pregnancies in the era of cell-free DNA screening

Abstract

Rates of diagnostic procedures in singleton pregnancies have declined since cell-free DNA (cfDNA) became commercially available. However, the impact of cfDNA on the uptake of diagnostic testing in twin gestations is unclear. We aimed to describe the rate of invasive diagnostic procedures in twin pregnancies after cfDNA screening with and without fetal structural abnormalities. This is a secondary analysis of data from a multicenter retrospective cohort study from 12/2011- 02/2020 that aimed to evaluate cfDNA screening performance in twin pregnancies. For this analysis, we excluded cases with a vanishing twin. cfDNA results were reported as positive, negative, or non-reportable. Structural abnormalities were defined as a major or minor anomaly, including an increased nuchal translucency >3mm. Rates of diagnostic testing were analyzed via chi-squared with odds ratio calculated by logistic regression. A total of 112 (6.6%) of 1,696 patients with twin pregnancies had cfDNA results and diagnostic procedures performed: 82 amniocenteses and 29 chorionic villus samplings (CVS). Diagnostic procedures were more frequent in patients that were older, had private insurance and conceived via IVF (Table 1). Patients with diagnostic testing were more likely to have positive or non-reportable cfDNA results compared to those without diagnostic testing. As noted in Figure 1A, 50% of positive cfDNA, 4.8% of negative cfDNA and 20% of non-reportable cfDNA ultimately had diagnostic testing. Figure 1B details the frequency of diagnostic procedures performed for each combination of cfDNA result and the presence of a structural abnormality. Diagnostic testing was more common if a structural abnormality was present (15.0% vs 4.5%, aOR 4.30 95% CI 2.71-6.83) and if there was an abnormal cfDNA result (32.8% vs 4.7%, aOR 8.72 95% CI 5.16-14.74), when adjusted for demographic factors. Cell-free DNA results and the presence of structural abnormalities greatly impact the decision to pursue diagnostic testing in patients with twin gestations.View Large Image Figure ViewerDownload Hi-res image Download (PPT)