In rare cases, male infertility is caused by a genetic disease like cystic fibrosis. In females, infertility is usually an ovulation disorder. Other causes of female infertility can be as a result of blocked fallopian tubes associated with endometriosis or pelvic inflammatory disease. In most cases, reduced fertility in one or both partners is the cause of infertility. This results in a term doctors use, called subfertility, which means that the couples attempts to conceive are difficult or delayed.
Primary infertility describes couples who are unable to have any children.
In contrast, secondary infertility is a term to describe couples who are able to produce a first child, but then have difficulty conceiving more children. Sometimes, impotence and sterility are confused with infertility. In fact, these two terms are not related to infertility. Impotence is the inability of the male partner to achieve or maintain an erection, thus preventing copulation. Sterility is very rare and is defined as the inability of the female partner to become pregnant or the male partner to produce sperm that is capable of impregnating.