This prospective, randomized study with control group was carried out at the Department of Obstetrics and Gynecology, Ioannina University School of Medicine (Ioannina, Greece). The study population consisted of 120 infertile women (more than a year of sexual attempts), aged 29-38 years, with laparoscopically documented endometriosis referred to the In Vitro Fertilization (IVF) Unit of the Department for infertility treatment during a 7-years period (May 2004 to September 2010). In addition, in the current study, we used 60 women with tubal infertility, documented by laparoscopy, without prior history of ovarian surgery, hydrosalpinx, and/or endometriosis as control group. This group was used to see if endometriosis affect the women's fertility. The participant's enrolment was made by three following authors A.K., K.Z., and M.P. During laparoscopy, the endoscopist documented the extension of the disease, the distribution of endometriotic lesions into the peritoneal cavity, and the presence/absence of active endometriotic lesions (red vascularized areas). All visible active endometriotic lesions were cauterized with bipolar diathermy. Women with sonographic evidence of ovarian endometrioma \> 2 cm in mean diameter, with early follicular phase serum Follicular Stimulating Hormone (FSH) levels \> 12 mIU/ml were excluded from the study. Cases of male factor infertility defined as a concentration of motile sperm less than 10 x 106 /ml and sperm with normal morphology less than 4% (Kruger, strict criteria) were also excluded from the study.

All women who decided to undergo an IVF-Embryo Transfer (ET) attempt were randomized into two groups according to administration or not of GnRH-a treatment, post-laparoscopy. The randomization is performed by accessing a central internet-based randomization program. The random allocation sequence and the assignment of the participants to interventions were made by the first author of the study (A.K.). The first group (Group A) was consisted of 60 women who received a depot preparation of a GnRH-a, 3.75 mg s.c, (leuprolide, Daronda depot, 3.75, Abbott, Hellas) every 28 days for three injections. The investigators preferred to pre-treat study patients with a long-acting GnRH-a for a period of 3 months because it has already reported that pregnancy rates after IVF-ET are similar in patients with endometriosis who are pre-treated with a GnRH-a for 10 to 90 days or greater than 90 days (Caruso 1997; Surrey et al., 2002). In this group, laparoscopies were performed 4 to 6 months prior of any cycle initiation for infertility. The second group (Group B) was consisted of 60 infertile women with endometriosis who did not receive the long-acting GnRH-a. All women were comparable regarding mean age, BMI, and duration of infertility.

All women of control and of group B, underwent controlled ovarian hyperstimulation (COH) after down-regulation with a GnRH-a (leuprolide, 20 IU/day, Daronda, 2.8, Abbott, Hellas) in a long protocol with a mid-luteal start. Administration of recombinant follicle stimulating hormone (rFSH, Gonal-F, Serono, Geneva, Switzeland) was started after at least 14 days of leuprolide therapy and when serum estradiol (E2) had been less than 100 pmol/l and when the thickness of the endometrium was less than 5mm. Down-regulation in women of group A was initiated 30 to 45 days after the third GnRH-a injection. A starting dose of 150 IU of follicle stimulating hormone (rFSH, Gonal-F, Serono, Geneva, Switzerland) was adjusted individually from day 6 of the cycle according to estradiol (E2) values and ultrasonographic follicular measurements. An ovulatory dose of human chorionic gonadotropin (HGG) (Pregnyl, Organon, Oss, The Netherlands) 5,000-10,000 IU was administered I.M. when mean diameter of an average of two to four follicles was larger than 16mm and the plasma estradiol concentration was higher than 1500 pmol/l.

All women were provided to luteal-phase support with natural micronized progesterone (Ultrogestan, Faran, Athens, Greece), 600 mgr daily vaginally in three divided dosages, starting the day after embryos transfer.

Follicular fluid sampling, oocyte collection and IVF Follicular fluid (FF) samples were collected during oocyte retrieval. From each patient, follicular fluid was sampled from the first one to three mature follicles, having a diameter of 18-20mm. Tumor Necrosis Factor(TNF)-a, Interleukine (IL)-1β, IL-6, IL-8 and IL-1-ra were measured in the FF of all women (secondary outcome measures). To prevent any cytokine alterations, only blood-free samples were used. IVF was performed in all cases. The fertilization rates were estimated for every woman 24 hours after oocyte retrieval (primary outcome measure).

Embryo grading and transfer The embryo quality and the clinical pregnancy rate were also primary outcome measures. Embryo development was evaluated 2 days after oocyte pick-up. The number of blastomeres and the proportion of embryo volume occupied by fragments were used for the evaluation. Embryos with \< 10%, \< 10-20%, \< 20-30% and \>30% fragments were estimated as grade 1,2,3 and 4, respectively. Three embryos with the highest blastomere number and the best morphology were transferred in each cycle. The remaining high-grade embryos were cryopreserved the same day.

Pregnancy was diagnosed by quantitative β-hCG, two weeks after embryos transfer. Clinical pregnancy was confirmed by observing fetal cardiac activity on transvaginal ultrasound four weeks after a positive pregnancy test. The clinical pregnancy rate and the quality of embryos were estimated in all women. The pregnancy rate was defined as the presence of sonographically visualized cardiac activity per cycle initiated.