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Introduction: Recurrent copy number variants (CNVs) curated by the Clinical Genome Resource (ClinGen) represent well-characterized genomic intervals with established associations to neurodevelopmental and other phenotypes.However, CNVs with low penetrance and variable expressivity present significant interpretive challenges in the prenatal setting, where the phenotypic implications may be uncertain.Inconsistent laboratory practices in the classification and reporting of such variants can further complicate prenatal counseling and clinical decision-making.To address this, we conducted a collaborative study to assess how clinical laboratories classify and report low-penetrance recurrent CNVs and to identify opportunities for alignment within prenatal genomic interpretation frameworks.Methods: Five clinical laboratories (Quest Diagnostics; Cedars-Sinai; University of California, San Francisco; University of California, Los Angeles; and Labcorp) participated in a comparative review of 31 ClinGen recurrent CNVs.Each CNV was characterized based on genomic coordinates, OMIM syndromic associations, gene content, and ClinGen dosage sensitivity scores.Participating laboratories submitted their current classification and reporting approach for each CNV.These were compared across sites and evaluated in the context of ClinGen postnatal interpretation guidance.Results: Consistent classification was observed for many CNVs, particularly those with well-established clinical significance.However, several areas of inter-laboratory variability were identified: (1) reporting of deletions involving autosomal recessive genes varied, with some laboratories reporting only homozygous findings, and others reporting heterozygous deletions if clinically relevant; (2) terminology for CNVs with low penetrance varied across laboratories; some referring to them as 'risk alleles' without further classification, while others reporting the same variants as pathogenic or likely pathogenic; and (3) practices surrounding the reporting of variants of uncertain significance (VUS) were inconsistent, with some laboratories excluding these from prenatal reports entirely and others including them with interpretive caveats.Inconsistencies may also result from differences in laboratory settings and client requests.Conclusion: This alignment initiative underscores both the progress and ongoing challenges in achieving consistent interpretation and reporting of lowpenetrance CNVs in prenatal genomic testing.The findings highlight the importance of shared terminology, standardized criteria, and ongoing inter-laboratory collaboration to ensure transparent, evidence-based reporting that supports clinical care and patient counseling.