Infertility is the failure of a couple to conceive after trying to do so for at least one full year. In primary infertility, pregnancy has never occurred. In secondary infertility, one or both members of the couple have previously conceived, but are unable to conceive again after a full year of trying.
The fertility of a couple depends upon several factors in both the male and female partner. Among all cases of infertility in developed countries, about 30 percent can be traced to male factors, 33 percent can be traced to female factors, 33 percent can be traced to factors in both the male and female partners, and 4 to 5 percent cannot be traced to obvious factors in either partner.