The purpose of this study is to determine if corifollitropin alfa (long-term gonadotropin administration) is effective in a controlled ovarian stimulation protocol in oocyte donors compared to daily gonadotropin administration (recombinant FSH or HP-hMG)

In recent years, increasingly advances have been developed in terms of controlled ovarian stimulation protocols. These improvements have also moved into the way of administration of the different treatments, and at present, with subcutaneous devices, it is possible to offer advantages such as the ability to ensure administration of the correct dose or modify the dose before charging.

Simplification of ovarian stimulation protocols can help to reduce physical stress of the donors and the cancellation rate. The need for daily injection does not worsen the degree of compliance, but it generates some anxiety related to the administration of the right dose and / or the possibility of making a unconsciously mistake . Innovations in delivery devices could help reduce the stress associated with the stimulation itself and improve the welfare of the donor. Given these considerations, the need to develop a stimulation protocol that reduces the physical and emotional burden of reproduction treatment is established.

Corifollitropin alfa molecule is a full-length recombinant FSH generating a sustained effect of stimulation; a single subcutaneous injection of this drug is able to replace the first seven injections of any daily FSH preparation, so finally, the result would be an overall decrease in the number of injections needed for the whole cycle. Pharmacological and pharmacodynamic characteristics of corifollitropin alfa could facilitate the design of simple stimulation protocols and the need for fewer resources when monitoring the donor, including fewer clinic visits.

Inclusion Criteria:

• Women aged 18-35 years who meet the entry criteria for the IVI Donor Program:
• Weight < 60 Kg
• Women with at least 6 antral follicles per ovary
• Women who will fit the protocoo during the period of the study
• Women who give written consent to participate in the test

Exclusion Criteria:

• Women with basal antral follicle count above 20 or below 6.
• Women with comorbidities, in the judgement of the investigator, that may interfere with the trearment of ovarian stimulation.