Strengths and limitations
In this study, we found, for the first time, that women with PCOS phenotypes A and D had an elevated risk of abortion after FET. This information will, for the first time, help clinicians develop individualised treatment plans to optimise ART outcomes. However, the investigation of several risk factors, such as environmental factors, physical activities and social factors, could not be included in this study. Due to the retrospective nature of this study, data on insulin resistance is lacking, and so was not included in the analysis. In addition, although we have the advantage of a large sample size, a large difference between groups was observed. Therefore, a further, large-scale and rigorous prospective validation study is necessary in future.