Reproductive endocrinologists, the doctors specializing in infertility, consider a couple to be infertile if:

* The couple has not conceived after 12 months of contraceptive-free intercourse if the female is under the age of 34
* The couple has not conceived after 6 months of contraceptive-free intercourse if the female is over the age of 35 (declining egg quality of females over the age of 35 account for the age-based discrepancy as when to seek medical intervention)
* The female is incapable of carrying a pregnancy to term.
* A couple that has tried unsuccessfully to have a child for a year or more is said to be sub-fertile meaning less fertile than a typical couple. The couple's fecund ability rate is approximately 3-5%.

Many of its causes are the same as those of infertility. Such causes could be endometriosis, or polycystic ovarian syndrome.