In vitro maturation (IVM) is a technique for obtaining potentially fertilizable oocytes from immature oocytes. An oocyte must be mature both nuclearly and cytoplasmically in order to be competent in the reproductive process. Nuclear maturation involves an oocyte in metaphase II stage and is easily evaluated for its morphology. However, cytoplasmic maturation can only be evaluated by in vitro fertilization of that oocyte. A mature nuclear and cytoplasmic oocyte is the one capable of producing a viable embryo. This study aims to optimize the in vitro maturation (IVM) technique to achieve nuclear mature oocytes, i.e., to mature the oocytes up to the metaphase II stage. In addition, an artificial oocyte activation (AOA) will be carried out to check the cytoplasmic maturation of the oocytes, avoiding the generation of potentially viable embryos.

This study corresponds to a second phase of the pilot study for the development of this technique in our IVF laboratory. We will use all we have learned in the first phase, as well as the experience acquired, to advance in the optimization of this protocol.

The correct functioning of this IVM technique would mean a reduction in the costs of ovarian stimulation treatments, as lower doses and shorter stimulation times are required, which implies lower risks for women derived from the medication and less stress for them.

-Inclusion criteria:

Women between 18-35 years old who have belonged to the egg donation program. Donors who agree to participate in the study after informing and signing the Informed Consent.

Documented previous good response to ovarian stimulation (at least 10 total oocytes and/or 8 MII).

Donors with at least one previous donation cycle, in which all oocytes obtained were freshly fertilized.

Donors who have already done all their donation cycles allowed by law. No personal or family history of interest.

From the medical point of view:

Body mass index between 18-25 kg/m2. Normal uterus and ovaries, without organic pathology. No polycystic ovaries Antral follicle count (AFC) >12 in the sum of the two ovaries on day 2-3 of the menstrual cycle. Normal karyotype Negative screening for infectious diseases (Hepatitis B virus, Hepatitis C virus, Human Immunodeficiency Virus and Syphilis). General analysis with hemogram, hemostasis and biochemistry with parameters within normality.

-Exclusion criteria:

Any systemic or metabolic disorder that contraindicates the use of gonadotropins.

Any medical condition that implies non-inclusion in the oocyte donation program.

Taking hormonal contraceptives within the last 3 months.