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 examined.

DESIGN

Three cohorts of idiopathic infertility couples undergoing 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 of excess follicle numbers; and a "direct IVF" group, patients proceeding directly to IVF-ET were compared.

SETTING

A tertiary referral reproductive medicine unit.

PARTICIPANTS

Forty-one idiopathic infertility couples.

INTERVENTION

In vitro fertilization-ET.

MAIN OUTCOME MEASURES

Number of oocytes retrieved, percent oocytes fertilized, number embryos per ET, implantation rate, percent pregnancy per cycle.

RESULTS

The cohorts had similar fertilization rates and mean (+/- SD) number of pre-embryos transferred. The conversion group demonstrated a higher pregnancy rate (PR) per cycle and a higher E2 concentration than the other groups. The PR of 35.0% in the direct IVF group appeared higher 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 etiologies for a large proportion of idiopathic infertility couples. However, as the conversion group demonstrated both a significantly higher E2 concentration ([E2]) and per cycle PR than the other cohorts with similar fertilization and pre-embryo transfer rates. Subjects converted in a COH-IUI cycle to IVF-ET are thus either more likely to produce pre-embryos more genetically capable of continued development to implantation stage (i.e., better oocytes recruited and fertilized) or due to the higher [E2] to have endometrium more receptive to implantation. Neither undiagnosed tubal factors nor fertilization problems appear to be major etiologic contributors.