AIMS: To evaluate the rate of trisomies and other chromosome abnormalities after positive ultrasound findings in first and second trimester. METHODS: In this study authors investigate the chromosome abnormalities detected in cases with prior abnormal ultrasound findings. During a ten-year period there were 1907 invasive interventions carried out with the purpose of chromosome analysis. The invasive intervention was genetic amniocentesis in 1619 cases and chorion villus sampling in 288 cases. RESULTS: Karyotyping revealed 103 cases (5.4%) with chromosome abnormalities. Abnormalities with subcutaneous oedema were examined: abnormal karyotype was found in 20% of cases with non-immune hydrops, 48.1% of cases with cystic hygroma, and 53.8% of cases with non-immune hydrops and cystic hygroma altogether, 8.3% of cases with nuchal oedema in the 1st trimester, and 5.5% in the 2nd trimester. The incidence rate of chromosome abnormalities in cases with cerebral anomalies was 6.3% of cases with ventricular dilatation, 3.6% of cases with choroid plexus cysts, and 15.9% of cases with other cranial anomalies. Regarding abnormalities of the heart; isolated echogenic intracardiac focus and ventricular septal defects were not associated with chromosome abnormality, but, in conjunction with other positive ultrasound findings the incidence rate of chromosome abnormalities were 7.9% and 26.7%, respectively. Other anomalies of the heart and large blood vessels showed an abnormal karyotype incidence rate of 18.2%. In cases of unilateral pyelectasis unassociated with other anomalies, the incidence rate of the chromosome abnormalities was 1%. In cases of bilateral pyelectasis, or pyelectasis associated with other anomalies, the incidence rate was 3%. In terms of anomalies of the abdominal wall and the abdomen; the incidence rate of association with chromosome abnormalities was 9.5% in cases with omphalocele, 11.8% in cases with duodenal atresia, and 5.7% in cases with echogenic bowel. In cases with short femur and humerus the rate of abnormal karyotype was 16%. CONCLUSIONS: Ultrasound plays important role in prenatal screening and diagnostics. In cases with positive ultrasound findings, the performance of karyotyping is reasonable.