Unexplained infertility: Defining the problem and understanding study design

Unexplained infertility is still a somewhat nebulous diagnosis of exclusion that is made when a couple is involuntarily infertile and no abnormalities are revealed by a standard infertility evaluation. Current research efforts are directed at identifying new causes of infertility and trials of empiric therapy. A fundamental problem with the study of unexplained infertility is the lack of a standard diagnostic protocol; therefore different investigators employ different criteria to make the diagnosis. It is difficult to compare results from different studies when the characteristics of the study populations differ or when couples are followed for different lengths of time. Additionally, the lack of an untreated control group in many treatment studies makes it difficult to interpret and compare the success of various treatments.