BACKGROUNDThere is currently no consensus about indications for surgery for infertility associated with colorectal endometriosis. The aim of this study was to evaluate cumulative pregnancy rates (CPRs) after ICSI-IVF cycles in patients with colorectal endometriosis and to identify determinant factors of fertility outcome.METHODSProspective longitudinal multicentre study from January 2005 to June 2011. We included 75 patients with colorectal endometriosis and proved infertility without prior surgery for deep infiltrating endometriosis. Univariable analysis was used to identify determinant factors of pregnancy rate. CPR was calculated using cumulative-incidence methods from log-rank test and Kaplan-Meier curves. For multivariable analysis, Cox proportional hazards model was used.RESULTSFor CPR per patient analysis, the total number of cycles was 113 and the median number of cycles per patient was 1 (range: 1-3). In the whole population the CPR per patient after three ICSI-IVF cycles was 68.6%. The CPR for patients with or without associated adenomyosis was 19 and 82.4%, respectively (P= 0.01). In addition, a patient age over 35 years (P= 0.02) and anti-Mullerian hormone serum level under 2 ng/ml (P= 0.02) were associated with a decreased CPR per patient. At multivariable analysis, adenomyosis [HR = 0.34, 95% CI (0.12-0.99), P= 0.49] was associated with a decreased CPR.CONCLUSIONSOur data confirm that ICSI-IVF offers a high CPR per patient. However, determinant factors of CPR should be taken into account when informing couples of their options.