The authors present a study of prenatal diagnostic interventions in a public hospital. The invasive prenatal diagnosis can be achieved by means of threee methods, aspirative punction of chorionic villous, extraction of amniotic fluid and fetal blood sample. Samples of chorionic villus are empoyed for citogenetic study, determination of the fetal cariotype or realization of a specific determination through technic FISH (Fluorescence in situ hybridization) or molecular genetics. Sample of amniotic fluid consists in the aspirative puncture under direct sonographic control of the amniotic cavity. During the period of the study, 9457 obstetric sonographies were performed with 121 genetic consultations of whom 46 resulted in invasive prenatal diagnostics. The results obtained are discussed (AU)