Poor ovarian response to stimulation in IVF cycles is a challenging and frustrating condition, due to its poor prognosis in terms of chances of pregnancy and live births. Various ovarian stimulation regimens have been tried to overcome these obstacles. A simple approach is increase the dose of the gonadotropin administration, but the results in terms of pregnancy rate are very low Another commonly used stimulation regimen is the microdose GnRH agonist protocol, which takes advantage of the initial rise in endogenous gonadotropins that follows the agonist administration in the early follicular phase and subsequently prevents a premature LH surge, with fewer cycle cancellations. However, their application in poor responders, even if in small doses and for a limited period, has been questioned as they may cause oversuppression of ovarian function, leading to a prolonged cycle and increased treatment costs without improving the outcomes.

Recently, GnRH antagonists were introduced in ART treatment. They are effective in preventing a premature LH surge and allow for a more natural recruitment of follicles in the follicular phase in a non-suppressed ovary, offering a potential alternative in the treatment of these patients. However, randomized studies evaluating the efficacy of this regimen in poor responders did not show any improvements in pregnancy rates. Current approach have included the addition of oral agents such us clomiphene citrate (CC) to gonadotropins. Some authors have investigated the role of CC in addition to low dose of gonadotropins in mild stimulation regimen, demonstrating that, despite a small number of retrieved oocytes, good quality embryos were produced with a subsequent improvement in the fertilization rate, clinical pregnancy rate and live birth rate. The only study that evaluate the efficacy of CC in addition to high doses of gonadotropins in poor responders showed improving in number of retrieved oocytes, transferred embryos and biochemical pregnancy; however, clinical pregnancy rate and live birth rate remained low and showed no measurable increase.

The aim of this study was to compare the efficacy of the CC as an adjunctive to a high dose of gonadotropins in cycles with antagonist protocols with the microdose GnRH agonist and flexible antagonist protocols in women who responded poorly to ovarian stimulation, to determine whether this protocol may improve IVF outcomes, offering a valid alternative in poor responder patients treatment.

Inclusion Criteria:

• poor responders in a previous IVF cycle at least 3 months before at our center and undergoing a new IVF attempt with at least two of the following criteria : I) age > 40 years old; II) basal follicular stimulation hormone (FSH) > 12 mIU/ml; III) three or fewer oocytes retrieved in the previous IVF cycle; IV) low estradiol levels on the day of human chorionic gonadotropin (hCG) administration (< 1500 pmol/ml).

Exclusion Criteria:

• body mass index > 30
• biochemical and ultrasound evidence of polycystic ovary syndrome
• stage III-IV endometriosis
• inflammatory or autoimmune disorders
• metabolic disease
• infertility medications within the past two months