The aim of this clinical trial is to evaluate the efficiency of two fertilization techniques used in Assisted Reproduction: conventional In Vitro fertilization (cIVF) and Intracytoplasmic Sperm Injection (ICSI), in terms of in-vitro and clinical results, in non-male infertility patients, comparing them in sibling oocytes.

The main questions it aims to answer are:

Does ICSI result in better fertilization rate, blastocyst rate or usable blastocyst rate? Does ICSI result in better pregnancy, clinical pregnancy and live birth rates?

Researchers will compare cIVF to ICSI in sibling oocytes to assess if a technique offers better results.

Participants undergoing an IVF/ICSI cycle will have their oocytes randomly divided in two groups: the oocytes from one group will be fertilized using cIVF and the oocytes from the other group using ICSI.

It is a prospective randomized study performed in the Reproduction Unit of Hospital Clinico San Carlos, in Madrid.

The study involves In Vitro Fertilization cycles with at least 6 oocytes retrieved and with normal semen parameters according to WHO.

The objective is to compare conventional In Vitro Fertilization (cIVF) and Intracytoplasmic Sperm Injection (ICSI) in sibling oocytes from the same cohort.

The oocytes obtained after the ovum pick up will be randomly divided in two groups and the fertilization technique (cIVF or ICSI) will be randomly assigned to each group.

Maturity stage, fertilization and embryo development to blastocyst will be individually recorded for every oocyte. Additionally, the destination of every embryo (transferred, cryopreserved or discarded) will be registered. This decision will be based just on embryo quality, irrespective of the fertilization technique.

MII rate, blastocyst rate and usable blastocyst (transferred or cryopreserved) rate will be calculated for each group.

Additionally, embryo transfers will be performed in the fresh cycle or in the associated thaw cycles using the cryopreserved embryos. In every transfer, the technique used to obtain the transferred embryo will be registered.

The results of the embryo transfers will be recorded as pregnancy (positive beta-hCG 14 days after transfer), clinical pregnancy (diagnosed by ultrasonographic visualization of a gestational sac 4 weeks after transfer, including ectopic pregnancy) and live birth delivery (deliveries with at least one live birth). Pregnancy rate, clinical pregnancy rate and live birth delivery rate will be calculated for each group.

Inclusion Criteria:

• Patients with at least 6 fresh, own oocytes.
• Patients with culture to blastocyst stage for all the embryos.
• Non-male factor infertility patients: semen sample with a good progresive sperm count, appropriate for cIVF.

Exclusion Criteria:

• Patients not willing to sign the informed consent. Patients not understanding Spanish.
• Patients with severe endometriosis
• Patients with recurrent implantation failure: at least 2 miscarriages or at least 3 transfers with good-quality embryos without pregnancy.
• Patients presenting total fertilization failure or very poor results in any of the two techniques in previous cycles

Individual participant data that underlie the results reported in this article, after deidentification (text, tables, figures, and appendices).

Beginning 9 months and ending 36 months following article publication.

Who will be able to access the IPD: Investigators whose proposed use of the data has been approved by an independent review committee ("learned intermediary") identified for this purpose.

For what type of analysis: For individual participant data meta-analysis. How they will be able to access: Proposals should be directed to mariadolores.cuquerella@salud.madrid.org. To gain access, data requestors will need to sign a data access agreement.