Abstract: Objective To explore the types and distribution of abnormal karyotypes of amniotic fluid chromosomes, and detection rate of abnormal karyotypes with different prenatal diagnostic indications. 
Methods A total of 1 305 pregnant women with the prenatal diagnostic indications were selected for amniocentesis and analysis of amniotic fluid karyotype in the Maternal and Child Health Care Hospital of Baoding City. 
Results In 1 305 amniotic fluid samples, 92 abnormal karyotypes were detected, with the detection rate of 7.05%. Among them, 68 cases(73.91%) had abnormal number of chromosomes, and 24(26.09%) had structural abnormalities. The most common abnormal karyotypes were 21 trisomy(48.91%), followed by abnormal number of sex chromosome（23.91%). Among the single indications, the detection rate was the highest in high risk of non-invasive prenatal testing(NIPT)(50.00%), followed by chromosomal abnormalities in one spouse(38.46%). The group with advanced age combined with high risk of NIPT had a higher detection rate than that with only advanced age(P<0.001). 
Conclusion The karyotype analysis of amniotic fluid cells in pregnant women with different prenatal diagnosis indications in the second trimester could help to find the abnormal karyotype of the fetus and reduce the incidence of fetal birth defects. NIPT has a higher accuracy in screening fetal chromosome abnormalities. NIPT screening strategy should be considered as the first choice for advanced maternal age.

Key words: amniotic fluid, chromosome, karyotype analysis, birth defects