〔Abstract〕 Objective To investigate and summarize the types and distribution of abnormal chromosome karyotypes in amniotic fluid in 2689 pregnant women in the second trimester. Methods A total of 2689 pregnant women from January 2016 to December 2021 in the Prenatal Diagnosis Center of Shenzhen Second People's Hospital were selected as the research objects. Amniotic fluid was extracted and cultured by aseptic amniocentesis for karyotype analysis. Results A total of 268 cases of abnormal karyotypes were detected in 2689 pregnant women, the abnormal rate was 9.97 %. Polymorphic karyotypes with 123 cases, the polymorphism rate was 4.57 %. Among them, 210 cases were abnormal (including chimerism), the detection rate was 7.81 %. Structural abnormality with 58 cases, the detection rate was 2.16 %. Among the abnormal numbers, there were 98 cases with trisomy 21 syndrome, 16 cases of trisomy 18 syndrome, 2 cases of trisomy 13 syndrome, 2 cases of trisomy 20 syndrome, 1 case of trisomy 8 syndrome, 88 cases of abnormal number of sex chromosomes, 1 case of triploid and 2 cases of labeled chromosomes. Conclusion In the second trimester of pregnancy, the number of chromosome abnormalities in the fetus is mainly abnormal, among which the incidence of trisomy 21 syndrome is the highest, followed by sex chromosome abnormalities, and structural abnormalities can not be ignored. Chromosome karyotype analysis is the gold standard in prenatal diagnosis and has irreplaceable value in prenatal diagnosis.