Defective oocytes are not a common cause of unexplained infertility as determined by evaluation of sharing oocytes between infertile donors and recipients.

Purpose: To determine if defective oocytes or sperm may be a common etiologic factor in unexplained infertility.

Materials And Methods: A retrospective comparison of fertilization rates and pregnancy rates from infertile donors with unexplained infertility trying to conceive with in vitro fertilization-embryo transfer (IVF-ET) and their respective recipients, who shared the other half of the oocytes with the recipient's male partner for financial compensation was performed. Pregnancy rates from donors and recipients were also compared to other donor recipient pairs sharing oocytes from infertile donors with tubal or male factor or financially-compensated donors providing oocytes to two recipients.

Results: Pregnancy rates from infertile donors with unexplained infertility were comparable not only to their respective recipients but to other donor/recipient pairs that received oocytes from donors with tubal or male factor or financially-compensated donors. Fertilization rates were somewhat reduced in the infertile donors.

Conclusions: Abnormal embryos resulting from an oocyte or sperm defect do not appear to be a common cause of unexplained infertility. The possibility does exist that sperm may be an etiologic factor in reduced fertilization potential, which not only could be obviated by conventional oocyte insemination, but could be further improved by intracytoplasmic sperm injection (ICSI).