The authors report the results of 468 foetal karyotypes performed on amniotic fluid or foetal blood samples after ultrasound discovery of foetal anomalies. A total of 46 chromosomal aberrations (10%) were detected. The rates of anomalies vary considerably according to the alarm sign; very high (greater than 30%) in cases of multiple malformations, foetal hydrops or foetal death, low (less than or equal to 2%) in cases of poly- or oligohydramnios and foetal growth retardation without detectable malformation. In addition to these chromosomal diagnoses, further investigations enabled in 9 cases the diagnosis of genetic autosomal recessive disorders. Our results which are comparable with those reported in the literature, demonstrate the importance of prenatal diagnosis in cases of pathological pregnancies, with regard to obstetrical and perinatal management as well as to genetic counseling.