Incidental finding of unreported large duplication in F8 gene during prenatal analysis: Which management for genetic counselling?

Detection of incidental finding and variant of unknown significance (VUS) during prenatal diagnosis has particularly increased with the emergence of genetic tests such chromosomal microarray analysis (CMA). Many factors and clear guidelines need to be applied in the interpretation of the potential clinical consequences of unreported complex copy number variations (deletions/duplications). From a clinical case where an unreported and not completely intragenic duplication in F8 gene has been identified in a 12-week-old fetus without haemophilia A history documented in the family, we will examine and study the difficulties of interpretation and the challenges that the detection of such variant has on genetic counselling.