This study evaluates the effect of pretreatment with a multivitamin supplement with probiotics (Seidivid Ferty4®) on oocyte retrieval in normo-responder patients undergoing controlled ovarian hyperstimulation (COH) for oocyte donation, considering both the total number of oocytes retrieved and the number of mature oocytes retrieved, that is, in metaphase II (MII).

Patients will be recruited on the day they are going to start the egg donation program. The patient will start taking the study treatment (multivitamin supplement with probiotics or placebo) immediately after inclusion and will call the site to initiate the oocyte donation protocol approximately 30 days after enrollment. Throughout the COH period of the protocol the patient will continue taking the study supplement (or placebo), without interruption until the day of the GnRH-agonist trigger. The administration of the agonist will be as a single dose, 36 hours before follicular puncture for the retrieval of mature eggs. Then, the retrieved oocytes will be denuded and examined by light microscopy to assess their quality. The evaluation will carried out by two different embryologists, blinded to the study protocol.