Unexplained infertility.

Unexplained infertility is a nebulous diagnosis that is justified only after a thorough and meticulous investigation of both partners. Even if the five basic tests constituting the infertility investigation have not revealed an abnormality, there may be a specific cause. Diagnosing unexplained infertility in this setting is somewhat arbitrary. In such couples, spontaneous pregnancies have been reported, with an average cumulative pregnancy rate of 60% after three years. Some additional testing, however, is appropriate. Treatment of unexplained infertility, however, tends to be empiric if no cause is found. Our current therapeutic plan entails superovulation with intrauterine insemination for at least four cycles. A cycle fecundity in the range of 0.23 may be expected but is highly influenced by the woman's age, with cycle fecundity dropping to as low as 0.05 after age 40. Alternatives to superovulation and intrauterine insemination are direct intraperitoneal injection of sperm with or without oocytes and intrafollicular injection of sperm. Gamete intrafallopian transfer and in vitro fertilization (IVF) are appropriate after a trial of empiric therapy. Our preference is to carry out IVF because the knowledge that fertilization has occurred is important in that fertilization failure is a known cause of unexplained infertility.