This study aims to investigate the difference in the number of oocytes obtained by performing ovarian stimulation in follicular phase vs. luteal phase in a population of patients with previous suboptimal response.

This is a controlled randomized clinical study.

We aim to include 41 patients diagnosed with suboptimal response who will undergo an ovarian stimulation in order to vitrify and accumulate oocytes.

The main variable for evaluating the efficacy in this exploratory study will be the number of oocyte cumulus complexes obtained.

Inclusion Criteria:

• Meets Bologna criteria to be diagnosed as poor responder
• Less than 10 oocytes obtained in a prior controlled protocol of conventional ovarian stimulation
• Age < 41 years
• Body Mass Index (BMI) between 18 and 32 kg/m2
• Regular menstrual cycles between 21 and 35 days.
• Indication for in vitro fertilization
• Indication to start stimulation with 150mcg of corifollitropin alpha
• Presence of both ovaries
• Ability to participate and comply with study protocol
• Signing an informed consent form

Exclusion Criteria:

• Presence of follicles larger than 10 mm in the randomization visit
• Endometriosis stage III/IV
• Patients with less than 4 oocytes in previous ovarian stimulation and poor ovarian reserve parameters (as per Bologna criteria)
• Concurrent participation in another study