THE PREGNANCY RATES OF COHORTS OF IDIOPATHIC INFERTILITY COUPLES GIVES INSIGHTS INTO THE UNDERLYING MECHANISM OF INFERTILITY

Objectives: To determine causes of ''idiopathic'' infertility, the IVF -ET experience of three cohorts of couples with this diagnosis was exa mined. Design: Three cohorts of idiopathic infertility couples undergo ing IVF-ET: a ''failed IUI'' group, three previous controlled ovarian hyperstimulation (COH)-IUI cycles with no pregnancies; a ''conversion' ' group, patients converted during a COH-IUI cycle to IVF-ET because o f excess follicle numbers; and a ''direct IVF'' group, patients procee ding directly to IVF-ET were compared. Setting: A tertiary referral re productive medicine unit. Participants: Forty-one idiopathic infertili ty couples. Intervention: In vitro fertilization-ET. Main Outcome Meas ures: Number of oocytes retrieved, percent oocytes fertilized, number embryos per ET, implantation rate, percent pregnancy per cycle. Result s: The cohorts had similar fertilization rates and mean (+/-SD) number of pre-embryos transferred. The conversion group demonstrated a highe r pregnancy rate (PR) per cycle and a higher E(2) concentration than t he other groups. The PR of 35.0% in the direct IVF group appeared high er than the 16.7% rate observed in the failed IUI group. Conclusions: Our observation of a lower PR in couples in the failed IUI group (16.7 %) than in couples in the direct IVF group (35.0%) suggests pre-embryo developmental problems or implantation problems as likely important e tiologies for a large proportion of idiopathic infertility couples. Ho wever, as the conversion group demonstrated both a significantly highe r E(2) concentration ([E(2)]) and per cycle PR than the other cohorts with similar fertilization and preembryo transfer rates. Subjects conv erted in a COH-IUI cycle to IVF-ET are thus either more likely to prod uce pre-embryos more genetically capable of continued development to i mplantation stage (i.e., better oocytes recruited and fertilized) or d ue to the higher [E(2)] to have endometrium more receptive to implanta tion. Neither undiagnosed tubal factors nor fertilization problems app ear to be major etiologic contributors.