Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (254 page)

   Infertility is defined as the inability to conceive after 12 or more months of regular intercourse without contraception.

   For a couple of normal fertility, the likelihood of pregnancy not occurring by 12 months is only 7%, which is close to the 5% figure often used as a threshold for a type 1 statistical error (here, falsely rejecting the null hypothesis of normal fertility). The likelihood of normal fertility decreases to 1% if pregnancy has not occurred after 3 years of intercourse without contraception. In a meta-analysis of 25 population surveys from 1991 to 2006, sampling 172,413 women, the 12-month prevalence rate of infertility ranged from 3.5 to 16.7% in more developed nations and 6.9 to 9.3% in developing nations.

   For those couples who have not been able to conceive despite 12 months of intercourse without contraception, a standard infertility evaluation is warranted for both partners. A two-part algorithm for the systematic assessment of the male partner is presented in Figure
7-2
.

   Although there is an uncertain relationship between abnormalities found on tests of infertility versus actual causes of infertility, one population-based study reported the following results for all factors of infertility (male and female combined):

   Male factors: 23%

   Ovulatory disorders: 18%

   Tubal damage: 14%

   Endometriosis: 9%

   Coital problems (e.g., impotence): 5%

   Cervical factors: 3%

   Unexplained: 28%

   Male factors of infertility can be divided into four general categories, of which the first three are amenable to laboratory diagnosis:

   Testicular disease (primary defects, including Y chromosome deletions) (30–40%)