The aim of this study is to assess the oocyte yield of infertile women with suspected or known poor ovarian reserve (POR) undergoing a GnRH antagonist protocol for IVF with Merional® starting either with a low (150 IU) or a high dose (450 IU) and adding 100mg of CC (Serophene®) in the early follicular phase of the stimulation (day 3 to 7). To date no RCT has been conducted to compare the reproductive outcome of patients with POR as defined by the ESHRE Bologna criteria after controlled ovarian hyperstimulation with HMG in an GnRH antagonist protocol using low doses versus high doses of HMG and adding CC versus placebo. We hypothesize that adding 100 mg of CC on day 3-7 to a HMG antagonist protocol will lead to an additional increment of endogenous GT thus increasing the oocytes yield after controlled ovarian stimulation due to higher endogenous gonadotropin secretion.

Inclusion Criteria:

• Age: >18 years < 43 years
• BMI: ≥ 18 ≤ 32 kg/m2
• Poor responder as defined by ESHRE working group

Exclusion Criteria:

• Age < 18 und > 43 years
• Pregnancy
• Breast feeding
• Uterine conditions interfering with endometrial proliferation and embryo implantation (submucous fibroids or polyps)
• Women diagnosed with PCOS according to the Rotterdam criteria
• Hyperprolactinaemia - untreated
• Both ovaries not accessible transvaginally for oocyte pick up
• Ovarian cysts of unclear dignity
• Evidence of hydrosalpinx on ultrasound
• Clinically significant severe systemic disease that are incompatible with pregnancy
• Known or suspected hypersensitivity to the active substances (gonadotrophins, ganirelix, progesterone, clomiphencitrate)
• Untreated thyroid or adrenal disorders
• Bleeding disorders
• Cancer
• Severe renal or hepatic dysfunction
• Necessity to take medication that could influence ovarian stimulation
• History of OHSS in prior IVF cycle