Seracchioli 2010a.

Study characteristics
Methods	No. of centres: 1 Location: Minimally Invasive Gynaecological Surgery Unit of S. Orsola University Hospital, Bologna, Italy Recruitment period: June 2002 to May 2006
Participants	Inclusion criteria: aged 20–40 years, 2 transvaginal ultrasonographic examination of ovarian endometrioma of which the diameter was ≥ 4 cm, at 6–8 weeks before surgery and on the day before surgery. Not attempting to conceive either at time of study entry or for ≥ 2 years after surgery Exclusion criteria: OCP for < 6 months before surgery; contraindications for OC; unwilling to tolerate the absence of menstruation; lack of the desire to postpone pregnancy for ≥ 2 years after surgery. No. randomized: 239 No. analyzed: 217
Interventions	Postsurgical medical therapy Group 1: non‐users Group 2: cyclic OC users – daily for 21 days, followed by 7‐day interval (low‐dose monophasic combined OC (ethinyl E2 0.020 mg and gestodene 0.075 mg daily), which started on the day of discharge after surgery and lasted for 24 months) Group 3: continuous OC users – continuous therapy no pill‐free interval (low‐dose monophasic combined OC (ethinyl E2 0.020 mg and gestodene 0.075 mg daily), which started on the day of discharge after surgery and lasted for 24 months)
Outcomes	Recurrence rate Recurrence‐free survival Size and rate of growth of recurrent cysts Time of recurrence
Notes	Power calculation: NR Funding: none declared Clinical trial registration number: NR
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated randomizations.
Allocation concealment (selection bias)	Low risk	Numbered, opaque, sealed envelopes.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	No placebo used. Blinding not mentioned.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	All scans were performed by experienced operators, blinded to the study allocation. All objective outcomes included in this study.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Group 1: 10 participants did not complete the study (4 spontaneous pregnancy, 6 started OC) = 12.6%. Group 2: cyclic users: 6 did not complete study (2 unrelated, 4 adverse events) = 7.6%. Group 3: continuous users: 6 did not complete study (2 unrelated, 4 adverse events) = 7.6%.
Selective reporting (reporting bias)	Low risk	All main outcomes are reported.
Other bias	Low risk	None detected. The 3 groups were homogeneous with regard to mean age, mean body mass index, endometriosis stage, mean endometrioma diameter, and the proportion of participants with bilateral cysts.