Background: Genetic and chromosomal causes in particular are responsible for a large percentage of pregnancy losses during the first trimester of pregnancy. Among chromosomal abnormalities, balanced or unbalanced, structural aberrations are the least common in reproductive disorders. The aim of the study: To describe several types of unusual structural chromosomal aberrations diagnosed by FISH in patients at high genetic risk. Materials and methods: Two patients were referred to the cytogenetics laboratory of the National Center of Medical Genetics from infertility clinic in the province of Pinar del Rio. Two patients, from Sancti Spiritus and Isla de la Juventud, with high genetic risk due to repeated miscarriages and advanced maternal age were referred to the laboratory for prenatal diagnosis. In the cytogenetic laboratory, conventional cytogenetic and FISH analyses were carried out. Conventional cytogenetic methods are used as the first tool in the diagnosis of chromosomal abnormalities. The FISH technique is used with VYSYS probes for specific labelling (LSI probes and CEP probes) of regions of chromosomes 5, 15, 13, 18, 21 and X, which completes the diagnosis. Results: In four women carrying structural rearrangements, the following chromosomal aberrations were detected: 47, XX,+ idic(15)(pter→q11.1::q11.1→ pter) .ish idic (15)(D15Z1++), 46,XX,t(13;21)(q22;q11.2), 46,XX,tas(18;21)(p11.3;q22.3) and 46,XY,inv(5)(p12q31.1). Conclusion: The present study is a demonstration of the importance of the FISH technology for the characterisation of subtle genomic aberrations causing reproductive disorders in female carriers. The effect of chromosomal aberrations, whether balanced or not, on the formation of altered germ cells that cause reproductive disorders has been discussed.