If a couple married for two years does not find any cause, they call it unexplained infertility. But this unexplained infertility can be of 3 categories. 1) The clinic or doctor did not find the cause. 2) The preliminary investigations did not reveal the cause and may require deeper investigations. 3) Sometimes, all investigations are not done at the same time. In such a situation, something may have changed though we assume it to be normal. In unexplained infertility, the most important aspect is to look deeper and see if we have missed any problems. Most of the time there is a cause for the delay in conception. One must try to find out the cause so that effective treatment happens.