Combined Z-scores to assess the impact of rare autosomal trisomies that results in non-invasive prenatal screening on pregnancy outcomes

This study aimed to combine Z-scores to evaluate the effects of rare autosomal trisomies (RATs) in non-invasive prenatal screening (NIPS) on pregnancy outcomes at a single center. We retrospectively collected the clinical data of women with high-risk RATs results using NIPS at a single center between January 2017 and December 2021. NIPS-positive results were separated into three groups based on the Z-value of RATs (Group1: 6 ≤ Z < 10; Group2: 10 ≤ Z < 15; Group 3: Z ≥ 15). Pregnancy outcomes of women with RATs were compared with the low-risk NIPS group. Overall, 83 RATs were identified in 23,321 NIPS results at our center. Prenatal diagnosis was conducted for 55 patients, and no case was confirmed, with a positive predictive value (PPV) of zero. Fifteen of these patients had adverse pregnancy outcomes, including delivered preterm and/or birth weight (9/15, 60.0 %), structural abnormalities (4/15, 26.7 %), miscarriage (1/15, 6.7 %), and intrauterine death (1/15, 6.7 %). There were 8 (8/22, 36.4 %) adverse pregnancy outcomes in Group 3, which was significantly higher than that in the low-risk NIPS group (p < 0.01). No significant difference was observed between the control group and Group 1 and Group 2 (p > 0.01). Clinicians should pay more attention to the RATs results when the Z-score is ≥ 15. The data are available for clinicians to guide the prenatal diagnosis of RATs and pregnancy management.