O61: Intragenic DMD duplications should not be presumed to be likely pathogenic: Findings from long-read sequencing

n=1,444/1,787), and 33.7% for egg donor cycles (n=1,033/3,067).Of TE samples with aneuploidy, 14,256 (75.2%) had at least one whole chromosome aneuploidy, 2,885 (15.2%) had at least one segmental aneuploidy, and 780 (4.1%) were complex abnormal with 5 or more aneuploidies.Of TE samples with segmental aneuploidy (n=2,885), deletions were identified in 1,947 (67.5%) and duplications in 1,066 (36.9%) ranging in size from approximately 10 Mb to over 100 Mb.Sixty-one recurring segmental aneuploidies were seen in more than five TE samples with 11 seen in 15 or more.Of note, many recurring segmental aneuploidies involved almost the entire p or q arm.Most TE samples (93.5%, n=38,390) were analyzed for mosaicism per provider request; 367 were analyzed for HM only and 38,023 were analyzed for LM and HM.Of TE samples analyzed for LM and HM, 4,535 (11.9%) had at least one mosaic finding; 4,203 (92.7%) had whole chromosome mosaic aneuploidy (22.6% with HM and 80.7% with LM) and 350 (7.7%) had mosaic segmental aneuploidy (40.0% with HM and 60.6% with LM).Of TE samples analyzed for HM only, nine (2.5%) had a single mosaic finding, all of which were whole chromosome aneuploidy.There were 2,662 TE samples with an isolated mosaic finding.The proportion of TE samples with an isolated mosaic finding was greatest in patients <35 years old (7.6%, n=1072/14153) and decreased as patient age increased (35-37 years: 6.6%, n=689/10,462; 38-40 years: 6.0%, n=489/8117; 41-42 years: 4.0%, n=133/3350; >42 years: 2.8% 49/1774; p < 0.001).Conclusion: These data are useful for demonstrating the rates of various chromosome findings in TE samples.This can be helpful for setting patient expectations for IVF cycle outcomes and providing post-test counseling regarding the frequency of chromosome errors that may be common in TE samples, but rarely seen in ongoing pregnancies or live births.