Currently, the optimal treatment to increase the chance of pregnancy and live births in patients with colorectal endometriosis and subfertility is unknown. Evidence suggests that that both surgery and in vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI) are effective in improving the live birth rate (LBR) among these women. However, the available evidence is of low quality, reports highly heterogeneous results, lacks direct comparison between both treatment options, and does not assess whether a combination strategy results in a higher LBR compared to IVF/ICSI-only treatment. Additionally, the optimal timing of surgery within the treatment trajectory remains unclear. The primary objective of the TOSCA study is to assess the effectiveness of surgical treatment (potentially combined with IVF/ICSI) compared to IVF-/ICSI-only treatment to increase the chance of an ongoing pregnancy resulting in a live birth in patients with colorectal endometriosis and subfertility, measured by cumulative LBR. Secondary objectives are to assess and compare quality of life and cost-effectiveness in both groups. Patients will be followed for 40 months after inclusion or until live birth. The TOSCA study is expected to be completed in 6 years.