Spontaneous abortions represent an important health and social problem. Studying the genetic causes of early pregnancy losses enlightens upon the critical stages of fetal development and submits important information for genetic counseling of affected families. The aim of our study was to: . find out the frequency and the type of chromosomal aberrations in spontaneously aborted pregnancies in Bulgarian population; . find out if there is some dependence between the type of observed chromosomal change and the time at which the pregnancy was lost; . find out if the type of chromosomal aberration is correlated to advanced maternal age, to abnormal ultrasound and to the clinical symptoms; We have analyzed 206 chorionic vilus probes of miscarriages using direct method for metaphase preparation and GTG-banding and/or classical CGH technique. The established frequency of chromosomal aberrations in spontaneously aborted pregnancies in Bulgarian population is similar to that observed in other populations. The progress of the pregnancy appears to depend negatively upon the presence of fetal chromosomal abnormality. There is no positive correlation between morphological abnormalities detected by ultrasound and the type of observed chromosomal change, but in the cases with trisomy an obvious fetal retardation was found.