Infertility (human)
Human infertility is the apparent inability to conceive and produce children during the normal childbearing years. In the health sciences, the term is defined on a limited and practical basis:"Infertility is defined as the inability of a couple to conceive within 1 year." ( Ashim Kumar, MD, Shahin Ghadir, MD, Niloofar Eskandari, MD, & Alan H. DeCherney, MD:Chapter 55 Infertility in Alan H. DeCherney and Lauren Nathan:Current Diagnosis & Treatment Obstetrics & Gynecology, 10th edition, Copyright © 2007 by The McGraw-Hill Companies, Inc). This definition means that couples who have tried to have a child for a year but have been unable to establish a pregnancy are eligible to be evaluated for infertility. When couples have had children in the past, but have not now been able to establish a pregnancy, medically they are said to have "secondary infertility". When the couple has never had a pregnancy, then the condition is called "primary infertility".
Some men and women are sterile, because of an instrinsic condition, these people cannot conceive. Sometimes that is a purposeful decision on their part, elective sterilization procedures are available to end fertility. Sometimes this is a congenital or acquired condition, that is not suspected or wanted. When neither member of a couple is sterile, but, on the other hand, the two are not able to easily establish pregnancy, they are called "subfertile". There are couples who are so extremely fertile that they are said to be "fecund", fecundity is the ability to achieve a pregnancy in just one menstrual cycle.
Infertile men, infertile women
Infertility can be due to one or the other of a couple, or the combination of the two. In the medical evaluation of infertile couples, "overall, an etiology for infertility can be found in 80% of cases with an even distribution of male and female factors, including couples with multiple factors." (reference for quote: Ashim Kumar, MD, Shahin Ghadir, MD, Niloofar Eskandari, MD, & Alan H. DeCherney, MD:Chapter 55 Infertility in Alan H. DeCherney and Lauren Nathan:Current Diagnosis & Treatment Obstetrics & Gynecology, 10th edition, Copyright © 2007 by The McGraw-Hill Companies, Inc). At the present time, that means that the remaining patients are given a diagnosis of "unexplained infertility", since no medical reason for their condition is revealed despite a full evaluation.