Cytogenetic investigation in 413 couples with spontaneous abortions

413 couples with one or more spontaneous miscarriages were karyotyped. Observed chromosomal rearrangements were classified as major rearrangements, i.e. Robertsonian and reciprocal translocations, pericentric and paracentric inversions, supernumerary small metacentrics, and minor rearrangements, i.e. pericentric inversions of chromosome 9, and constitutional fragility of particular chromosome sites. 2.30% of the individuals were carriers of a major rearrangement, which represents a ten-fold increase when compared to the general population. The contribution of each type of rearrangement is unequal, the most important being pericentric inversions (36 times more frequent than in the general population). Contrary to data from the literature, the probability of finding a rearrangement does not seem to increase with the number of miscarriages.