OBJECTIVE: To investigate the incidence of chromosomal abnormalities in early pregnancy loss after IVF and ICSI. DESIGN: Retrospective study. MATERIALS AND METHODS: From January 2004 to December 2007, a total of 166 cases of miscarriage villi samples after IVF-ET were collected for cytogenetic analysis. The average age of cases was 38.9. All IVF cycles were performed by natural cycle or mini IVF in our center. RESULTS: Cytogenetic results were obtained for 158 (ICSI 63, IVF 95) samples and 117 samples (74.1%) showed chromosomal abnormalities. Autosomal trisomies were detected in 80 samples (68.4%). In 80 samples, 22 samples were trisomy 22(27.5%), 17 samples showed trisomy 15 (18.8%) and 10 samples were trisomy 21 (12.5%). Double trisomy was detected in 13 samples. In 117 samples, 8 samples showed sex chromosome monosomy and all samples showed 45,X. Triploidy was detected in 1 sample and tetraploidy was detected in 3 sample. Structual rearrangements were detected in 8 samples (6.8%). Normal karyotype samples accounted for 41 (25.9%). ICSI samples more showed aneuploidy than conventional insemination patients; 82.5% vs. 68.4% (P<0.05). There was no difference of average age between two groups. Comparison between conventional insemination and ICSI did not show significant difference in the type of chromosome abnormalities. CONCLUSION: Chromosome abnormalities are identified in 74.1% of all spontaneous abortions. In this study, the average age of IVF patients is 39.5. Due to this background, incidence of abnormal chromosome of miscarriage villi showed higher than previous reports. In autosomal trisomy samples, incidence of trisomy 22 was particularly higher than other chromosome trisomies. Furthermore, the frequency of trisomy 15 was higher than previous reports. These results indicate that the proportion of chromosomal abnormalities may be different between normal pregnancy and IVF or ICSI. We also found that ICSI samples were more likely to have aneuploidy than IVF samples.