This study is a prospective ranzomized analysis including 372 human oocytes from 44 women. Half of the oocytes from the same patient will be randomly allocated to induce oocyte activation using two protocols: in protocol nº 1 we will use ionomycin (prepared solution), protocol nª2 A23187 (GM508 CultActive Gynemed) will be applied. Non treated oocytes will serve as control. Oocyte fertilization rates, embryo development and embryo quality will be analyzed. Obstetrics variables of offspring will be also followed and compared.

Background: Oocyte non-activation (OAD) is the main cause of fertilization failure in intracytoplasmic sperm injection (ICSI) cycles. Oocyte activation involves a series of consecutive events that take place in the oocyte during fertilization, triggered by the action of sperm-specific phospholipase C zeta (PLCz) that causes an increase in the amount of free Ca2+. This increase, as well as its transient elevations in space and time, is species-specific. Defects in this pattern of Ca2+ release and oscillation are attributed to most cases of OAD. Several strategies have been described and applied to achieve artificial oocyte activation (AOA), which use mechanical, electrical, or chemical stimuli, among which the use of calcium ionophores such as ionomycin and A23187 (calcimycin) predominates. Documented fertilization and pregnancy rates appear to be improved in patients with previous low fertilization rates or total fertilization failures after using ICSI-AOA compared to conventional ICSI. However, the lack of well-designed studies, the heterogeneity of the population undergoing AOA, and the scarcity of results comparing different AOA protocols make it difficult to assess the clinical efficacy and safety of the technique.

Study question: In patients with prior fertilization failure or low fertilization rates (30% or less), does AOA improve reproductive outcomes compared to conventional ICSI in patients with prior fertilization failure? and if it does, which protocol is more efficient?

Inclusion Criteria:

• Own oocyte patients who have had previous fertilization failure in previous cycles.
• Own oocyte patients with fertilization rate in previous cycles less than or equal to 30% of the microinjected oocytes.

Exclusion Criteria:

• Oocyte Recipient Patients
• Sperm bank sperm recipient patients
• Patients who after oocyte decumulation have less than 2 mature oocytes.