The causes of infertility are wide ranging but can be examined in light of the reproductive cycle described in Question 1. (See Table 1.) In general, the causes of infertility can be equally divided between the male and female partners in a couple.

Table 1 Diagnoses Among Couples Who Had ART Cycles Using Fresh Nondonor Eggs or Embryos,* 2006

Cause of InfertilityPercent
Endometriosis5.1
Ovulatory dysfunction6.4
Other causes8.3
Diminished ovarian reserve9.2
Tubal factor9.8
Multiple factors, female only11.3
Uterine factor1.4
Multiple factors, (female + male)18.3
Male factor18.3
Unexplained cause12.0

* Total does not equal 100% due to rounding.
Source: Adapted from the Centers for Disease Control and Prevention. 2006 Assisted Reproductive Technology Success Rates, December 2009.

Half of all infertility cases, therefore, involve problems with the sperm of the male partner. Unfortunately, functional tests for sperm competence (the ability of sperm to fertilize an egg) are not available leaving us to rely upon the descriptive components of the semen analysis. A complete semen analysis should include the total number of sperm (concentration), the percentage of those sperm that are moving (motility), and the shape of those sperm (morphology).

Many factors can reduce the female partner’s ability to conceive. For example, a woman may have anatomical problems related to the fallopian tubes, uterus, and peritoneal structures within the pelvis such as adhesions or endometriosis. Problems with ovulation are very common in infertile patients, and women with irregular periods may suffer from a common disorder such as polycystic ovarian syndrome (PCOS). Another major fertility factor is reproductive aging. Peak fertility occurs when a woman is in her twenties, and it declines significantly during her thirties and forties. The rate of decline increases after the age of 35 as is evident in decreased IVF pregnancy rates and decreased embryo implantation rates in this age group.