During a 3 and 1/2 years, 132 pregnancies were diagnosed as having a wide variety of congenital abnormalities. A high resolution ultrasound and multidisciplinary approach was used. In 95 cases fetal karyotyping was made. In this group the incidence of chromosomal abnormalities diagnosed during the period and phenotypic expression of the different types of chromosomal abnormalities was investigated. 29 abnormal karyotypes were found; 11 trisomy 18, 7 in monosomy X, 4 in trisomy 21, 3 in trisomy 13, 1 with tetraploidy (92XXYY), 1 Turner mosaic (45XO 68% 46XY 32%), 2 inversions of choromosome 9. Of the total abnormal chromosomal diagnosed during the period (N = 57), this group represented 49.2%, compared to 5 to 15% found in other risk groups. 224 congenital abnormalities were found. 43 (19%) isolated, and 181 (81%) associated. Of the 224 congenital abnormalities diagnosed, 80 (36%) were associated with chromosomal abnormalities. The most associated markers were duodenal atresia, heart defect, microcephaly, enlarged posterior fossa, and cystic hygromata. A specific markers pattern was found for each aneuploidy; heart defects for trisomy 18, holoprosencephaly and faciel cleft for trisomy 13, and cystic hygromata for monosomy X. It was concluded that the ultasound can be the most useful method to select the group of pregnant women with a higher risk of abnormal karyotype.