Infertility in a couple is defined as the inability to achieve conception despite one year of frequent unprotected intercourse. Use of this time period, while arbitrary, was based upon a study of 5574 English and American women engaging in unprotected coitus who ultimately conceived between 1946 and 1956 . Among these women, 50 percent conceived within three months, 72 percent within six months, and 85 percent within 12 months.
One population-based study found the following distribution of causes when evaluating infertile couples  (see "Causes of male infertility"):
●Male factor – 23 percent
●Ovulatory dysfunction – 18 percent
●Tubal damage – 14 percent