ObjectiveTo investigate the chromosomal characteristics of blastocysts and pregnancy outcomes in patients with polycystic ovary syndrome （PCOS）， and to analyze the impact of PCOS on embryonic aneuploidy rate and the risk of miscarriage. MethodsThe retrospective cohort study was conducted on the preimplantation genetic testing（PGT） in the First Affiliated Hospital of Sun Yat-sen University， including cycles of PGT for aneuploidy（PGT-A） and PGT for monogenic disorders（PGT-M）. The 191 PCOS cycles（PCOS group） were matched with 564 control cycles（control group） using propensity score matching. The oocyte and embryo viability， chromosomal testing results of blastocysts， and cumulative clinical outcomes were compared between two groups. Subgroup analysis was performed by stratifying PCOS patients based on oocyte retrieval （＞20 vs. ≤20）. And the pregnancy outcomes after euploid embryo transfer were compared under different levels of ovarian response. ResultsPCOS group showed a significantly higher rate of aneuploidy per blastocyst compared to control group （21.8% vs. 19.0%， P=0.044）. Clinically， the overall miscarriage rate in the PCOS group was significantly higher than control group （17.2% vs. 10.3%， P=0.024）， even after euploid embryo transfer （17.2% vs. 10.0%， P=0.019）. In the PCOS subgroup with ＞ 20 oocytes ， the miscarriage rate following euploid embryo transfer was dramatically increased compared to control group （21.4% vs. 6.7%， P=0.001）， accompanied by higher risks of early miscarriage （15.7% vs. 5.7%， P=0.011）. Conversely， the PCOS subgroup with ≤ 20 oocytes showed outcomes comparable to control group. ConclusionsPatients with PCOS exhibit a significantly higher rate of blastocyst aneuploidy compared to the control group. Furthermore， PCOS is associated with a marked increase in miscarriage rates following blastocyst transfer， even with euploid embryos， particularly among patients with high ovarian response.