From Citizendium, the Citizens' Compendium
Human infertility occurs when men and women are unable to conceive and produce children during the normal childbearing years. In the health sciences, the term is defined on a limited and practical basis:"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 the couple has never had a pregnancy, then the condition is called "primary 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".
Some men and women are sterile, because of an instrinsic condition, these people cannot conceive. Sometimes that condition is a purposeful decision on their part, elective sterilization procedures are available to end fertility. Sometimes sterility is a congenital or acquired condition, that is not suspected or wanted. If one member of a couple is sterile, then that couple will be infertile no matter the mate's status. Except for elective sterilization, it is rare for a young adult to be completely sterile. Doctors who specialize in infertility suggest that, most commonly, it is "subfertility" that is a problem. 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", and again, that designation may more properly be attributed to just one or the other of the couple after medical testing is completed. At the other extreme of infertility, 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 (about 20% of these couples) are given a diagnosis of "unexplained infertility", since no medical reason for their condition is revealed despite a full evaluation. Physicians who specialize in infertility discuss "male factors" and "female factors" in their analysis. "Roughly 40% of cases involve a male contribution or factor, 40% involve a female factor, and the remainder involve both sexes."(reference for quote:Paul J. Turek, MD:Chapter 42. Male Infertility in SMITH'S GENERAL UROLOGY - 16th Ed. 2004 ISBN 0071396489)
Male factors in fertility
The male ejaculate of semen is the mainstay of evaluation for male factors. Since this semen is produced by the testis, and expelled through the ducts of the male reproductive system, characteristics in the ejaculate that are associated with infertility may have many underlying causes-ranging from the cellular maturation of the spermatozoon (the mature sperm cell) from spermatogonnia, to antibodies in the fluid of the ejaculate that inhibit the motility of sperm, to . Overall, male factors in infertile couples are found in a quarter to about 40% of cases. Sperm take about 74 days to mature, and the quality of a man's semen can change over time. Accordingly, sometimes semen samples are examined several weeks or months apart, to be sure that a finding is not missed, or that a temporary problem found in an initial specimen is not assumed to be permanent.
When semen samples show that a man is azoospermic, the underlying cause may have nothing to do with his actual production of sperm, but may reflect other problems-such as obstruction of ducts that transport sperm. "A male with less than 5 million sperm per milliliter warrants an endocrinologic evaluation including follicle-stimulating hormone (FSH), leuteinizing hormone (LH), and testosterone, or a karyotype in selected cases." ((Ashim Kumar, MD, Shahin Ghadir, MD, Niloofar Eskandari, MD, & Alan H. DeCherney, MD:Chapter 55Infertility in Alan H. DeCherney and Lauren Nathan:Current Diagnosis & Treatment Obstetrics & Gynecology, 10th edition, Copyright © 2007 by The McGraw-Hill Companies, Inc)
Female factors in fertility
The female role in establishing a normal pregnancy has to do several physiological processes: the production of a gamete (ovum) in the ovulatory cycle, the transfer of this gamete into the uterus through the fallopian tubes, and the implantation of an embryo in the lining of the uterus. Sometimes, a woman can establish a pregnancy, but has a spontaneous abortion, which also called a miscarriage, rather than delivering a baby. This may sometimes happen repeatedly, but if conception occurs, is not generally called infertility, unless the loss is so early in gestation that the pregnancies are not apparent.
- Problems in ovulation are found in about a quarter of the couples evaluated for infertility.
- Post-coital test (also called the Sims-Huhner test): This test has a rational basis and the results should be important establishing whether motile sperm are able to enter the uterus, but there has not been any actual clinical proof of whether the results of this test correlate with the ability to establish pregnancy. Among physicians, the use of this test is controversial. When it is carried out, the test is preferentially performed close to ovulation. Cervical mucus is aspirated 6-8 hours after coitus and examined under a microscope for spermatozoa; if there are fewer than 10 motile sperm per high-power field, then the results are abnormal. When a man's semen sample shows ample numbers of normally motile sperm, but the post-coital test is abnormal, the cervical mucus is sometimes said to be "hostile", however, the test's "value in assessing cervical hostility to sperm has never been proven".(reference:((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)
- Immunobead test (anti-sperm antibodies):The immunobead test is the antibody assay used in most labs, and is considered positive when only 20% or more of motile spermatozoa have immunobead binding. However, the test is considered to be clinically significant when 50% of sperm are coated with immunobeads.