Because ovarian sex steroids fluctuations during the menstrual cycle are implicated in the pathogenesis of the endometriosis-related chronic pelvic pain (CPP), the oral contraceptives (OCs) are used with non-contraceptive indication for this disorder.

To date, OCs are widely used as medical treatment in patients with endometriosis, in addition, they are recently experimented as post-surgical therapy. Traditional cyclic regimen, with 21 days of active pills with 7 days of placebo or suspension, is usually adopted. Furthermore, recent studies suggested that long-term continuous OCs use can be effective in the postoperative period both as second- and third- line treatments after cyclic regimen failure. In these studies a combined treatment with ethinilestradiol (0.02 mg) plus desogestrel (0.15 mg) were used and compared with baseline or ciproterone acetate.

A recent study showed a deeper ovarian and endometrial suppression with continuous OCs in comparison with cyclic OCs, providing a physiological rationale for continuous OCs use for noncontraceptive indications. Furthermore, to date, no study compared post-operative continuous versus cyclic OCs in patients with endometriosis-related CPP.

Premenopausal women with endometriosis-related CPP scheduled for laparoscopic surgery to our Academic Department of Gynecology will be consecutively enrolled. Subjects with hystologically confirmed endometriosis at laparoscopy (stage I-IV of the American Society Reproductive Medicine), a subjective severity of pelvic pain by using a visual analogue scale (VAS 1-100) of at least 70, and without immediate desire of pregnancy will be enrolled.

Briefly, all patients will undergo conservative laparoscopic surgery for endometriosis. Thereafter, a low-dose monophasic OC containing 2.0 mg clormadinone acetate plus 0.03 mg ethinil-estradiol (Belara®, Grunenthal, Milan, Italy) will be administered. Patients from the experimental group will be treated with a continuous regimen, while patients from the control group will receive the OC with a cyclic regimen consisting of 21 days of active pills with 7 days of placebo. The drug and the placebo will be similar and will be labelled according to the subject number. For the overall study-period, operators and patients will be blind to the treatment allocation.

Inclusion Criteria:

• Premenopausal state
• Endometriosis-related chronic pelvic pain
• Hystologically confirmed endometriosis at laparoscopy
• Subjective severity of pelvic pain by using a visual analogue scale of at least 70
• No immediate desire of pregnancy

Exclusion Criteria:

• Age ≤18 or ≥ 40
• Previous use of drugs for treating CPP (wash-out period of 3 months), with exclusion of non-steroidal anti-inflammatory drugs
• Contraindication to estro-progestin compounds
• Major medical diseases
• Psychiatric disorders
• Pelvic inflammatory disease
• Adnexal patologies
• Unability to complete the daily diary
• History of alcohol or other drugs abuse