[The involvement of the zona pellucida in unexplained infertile women]

Unexplained infertility (*UI) was a common problem before the IVF era. A couple was declared as UI only after they passed all the routine common tests and no reason was found for the infertility. The introduction of ICSI in the IVF clinics enabled the investigation of the quality of the couple's gametes. Thus, the definition of the term UI was refined and the number of couples encompassed by this term decreased dramatically. Zona Pellucida (ZP) incompetence was described as one of the causes of UI. We recently (2004) published a case study of an UI couple due to this cause. The oocytes of the woman collapsed during the preparation of the oocytes for sperm injection. These oocytes suffered from irregular ZP and abnormal appearance. Only after gentle treatment of the oocyte-cumulus complex and ICSI fertilization, embryo development and delivery of normal newborn was achieved. This woman and others who suffer from UI did not conceive in a natural way since the ZP of the ovulated eggs did not bind sperm cells and, thereby, were not fertilized. It only recently became possible to find the reason for the infertility of the couple and the solution, through the use of highly advanced technology in the IVF-ICSI process. One of the reasons for the deformatted ZP is the malfunction of the gene that encodes the 4 glycoproteins, which compose the ZP. This is now under investigation in our Institute.