Why are couples not getting pregnant?

Getting pregnant depends on both the woman and the man. A couple might not get pregnant because of a problem with the man’s body,the woman’s body, or both.
It is described as infertility when a couple has been trying for one year without success Tests are done by the Gynaecologist in both partners to try to find out the cause.But even with tests,the Gynae sometimes cannot find out why this is so.