Abstract： Background:When considering the issue of recurrence,perimenopausal women may have more dilemma during management comparing with young women,for example,whether to retain the uterus and ovary during surgery,whether it is necessary to add adjuvant medicine treatment after operation,and there is no evidence for reference about using of gonadotropin-releasing hormone agonist.This study aimed to study the risk factors for the recurrence of ovarian endometriosis (EM) in patients aged 45 and over.Methods:This is a retrospective nested case-control study.We reviewed the medical records of patients aged over 45 years who underwent surgical treatments for ovarian EM from 1994 to 2014,in Peking Union Medical College Hospital of Chinese Academy of Medical Sciences.By following up to January 2016,45 patients were found to have relapses and regarded as the recurrence group.The patients with no recurrence during the same follow-up period were randomly selected by the ratio of 1:4 as the nonrecurrence group (180 patients in total).Stratified Cox regression was used to analyze the risk factors of the recurrence.Results:Univariate analysis showed that there was a significant difference in the postoperative treatment (the percentage of patients who received postoperative treatment in non-recurrence group and recurrence group,23.9％ vs.40.0％,x2 =4.729,P =0.030) and ovarian preservation (the percentage of patients who received surgery of ovarian preservation in non-recurrence group and recurrence group,25.0 ％ vs.44.4％,x2 =19.462,P ＜ 0.001) between the nonrecurrence group and the recurrence group.There was no correlation between recurrence and the following factors including patient's age,menarche age,gravidity,parity,CA125 level,ovarian lesions,menopausal status,combined benign gynecological conditions (such as myoma and adenomyoma) and endometrial abnormalities,and surgical approach or surgical staging (all P ＞ 0.05).Multivariate analysis indicated that whether to retain the ovary was the only independent risk factor of recurrence for patients aged 45 years and over with ovarian EM (odds ratio:5.594,95％ confidence interval:1.919-16.310,P =0.002).Conclusion:Ovarian preservation might be the only independent risk factor of recurrence for patients aged 45 years and over with ovarian EM.