• Colorectal endometriosis defined as endometriosis involving the (colo)rectum:

• #Enzian classification score C1,C2,C3 (C=rectum) or FI (F=far locations, I=sigmoid colon) detected with ultrasound or MRI;

• Women in a heterosexual or in a same-sex relationship;

• The patient has an active wish to conceive and experiences at least one of the following criteria:

‣ At least one year of non-conception (either spontaneous of after intra uterine inseminations)

⁃ Inability to have timed intercourse because of pain (dyspareunia and/or chronic pelvic pain)

⁃ Severe complaints (expectant management is not acceptable (anymore)

• The patients has an indication for IVF/ICSI according to Dutch guidelines (Werkgroep netwerkrichtlijn, december 2010);

‣ failed intra uterine insemination

⁃ male factor subfertility (oligoasthenoteratozoospermia defined as VCM \<1 million)

⁃ bilateral tubal pathology (e.g. bilateral hydrosalpinx, bilateral tubal occlusion)

⁃ age \> 38 years and (unexplained) subfertility

⁃ severe endometriosis in case of subfertility

• The patient is faces the choice between IVF/ICSI or laparoscopic (colorectal) endometriosis or is on the waiting list for a respective treatment at T=0 (at the beginning of the treatment trajectory), T=1 (after one unsuccessful IVF/ICSI cycle) or T=2 (after 2 unsuccessful IVF/ICSI cycles)