Upon completion of the diagnostic evaluation, approximately 10% to 15% of couples will be found to have unexplained infertility, meaning that all of their tests are normal. Such couples are probably best called “subfertile,” and most can successfully conceive with IVF. Prior to the introduction of IVF, couples with unexplained infertility had a poor chance of achieving pregnancy with other treatment methods. Couples with unexplained infertility can consider IUI with or without fertility drugs prior to attempting IVF, but these treatments are much less successful than IVF. In addition, use of fertility drugs and IUI can be associated with an unacceptable high rate of multiple pregnancy, leaving patients confused about this approach to fertility treatment.

We do not know precisely why couples with unexplained infertility are infertile. Some evidence suggests that the source of the problem may be tubal dysfunction or sperm–egg interaction. Often, a fertility center uses IVF together with ICSI in such couples to ensure that fertilization of the ova occurs. Today, thanks to these techniques, couples with unexplained infertility have a very strong likelihood of ultimately achieving a successful pregnancy with IVF.