Infertility is the inability to conceive after at least one year of unprotected intercourse or 6 months in women 35 years of age and older. The 3 main cause of infertility are seen in about 80% of infertile couples: ovulation issues, sperm problems, and fallopian tube issues. Ina bout 15% of couples all tests are normal, that's "unexplained infertility".