Abstract: Objective: To analyze retrospectively the karyotypes of amniotic fluid, and to study the relationship between the distortion of chromosome number or structure and fetal abnormalities. Methods： 1 984 pregnant women with the high risks under prenatal screening were asked to test the karyotypes of amniotic fluid in their pregnant weeks of 17 to 23, with the informed consent. Results：In 1 984 cases, there were 49 cases （２．47％） with abnormal karyotypes, including 31 cases（１．５６％） with the number abnormalities （27 cases with autosome number distortion and 4 cases with sex chromosome number distortion）, 12 cases（0.60%） with the structural abnormalities（9 cases with the chromosome balanced translocation and 3 cases with unbalanced translocation） and 6 cases（０．３０％） with chimera. There were 226 cases（１１．３９％） with the chromosomal polymorphism mutation, including 20 cases (1.01%) with 9 chromosome percentric inversion, 78 cases（３．９３％） with the satellite and petit polymorphism mutation of D/G group chromosome, 72 cases（３．６３％） with the secondary constriction polymorphism mutation and 56 cases（２．８２％） with big or small Y chromosome. Conclusions：Karyotype examination of amniotic fluid is very important for the diagnosis of fetal chromosomal diseases, especially for those pregnant women with the high risks under prenatal screening. Besides, it is helpful to evaluate the pregnancy outcomes and fetal genetic health.

Key words: Prenatal diagnosis, Amniocentesis, Chromosome, Chromosome aberrations, Karyotyping