The study proposes new recommendations for classifying semen samples as "normal" or "abnormal," and if accepted by clinicians worldwide, the research could rewrite laboratory standards used for 50 years.
Lead author David Guzick, M.D., chairman of Obstetrics and Gynecology at the UR Medical Center, Rochester, N.Y., says the findings demonstrate in scientific terms what many clinicians already suspect -- that male infertility is not as clear-cut as the current laboratory guidelines suggest. For example, a sperm count may fall just below the laboratory criteria for infertility published by the World Health Organization. But in reality, that man may be able to establish a pregnancy. The study's new guidelines create a "gray zone," for such borderline semen samples.
"Every treatment for infertility depends upon first establishing what's normal and abnormal," Guzick says.
"Up until now, we've just been using guidelines without rigorously testing them. We hope specialists will use these revisions in their counseling of infertile couples and in tailoring treatments to individual patient circumstances."
The researchers are the first to compare fertile and infertile men using contemporary methods for semen analysis; other research has only gone so far as to study sperm from infertile men before and after treatment. The research is also the first to analyze semen samples from a very large cross-section of men: It evaluated samples from 765 men from infertile couples and 696 men from fertile couples, at nine locations across the country. All of the men were between 20 and 55 years old. The National Institute of Child Health and Human Development funded the research.
The results show there is no single criteria that always leads to infertility -- in fact, the shape and appearance of sperm (known as morphology) seemed to be a very important measurement for discriminating between fertile and infertile men, the study found. However, the guidelines currently used by clinicians and published in WHO laboratory manuals do not even provide a reference value for morphology.
About 1 in 6 couples are unable to conceive children. Of those couples, 30 to 40 percent suffer from male infertility. The routine test for diagnosing male infertility is a semen analysis. It consists of obtaining a sample, and then microscopically analyzing the number of sperm per milliliter, the percentage of sperm that are moving, and the shape of the sperm. Normal sperm are uniformly oval.
The World Health Organization says that a "normal" sample contains 20 million sperm per milliliter, with at least 50 percent of the sperm moving. Anything else is considered "abnormal."
But Guzick's study provides three new categories as reference points:
The exact cause of male infertility is unknown, although hormonal and anatomic factors are sometimes responsible, and certain behaviors, such as smoking cigarettes or marijuana, are associated with lower sperm counts. Treatment consists of intrauterine insemination (IUI), where a concentrated number of mobile sperm are extracted from a sample and injected into a woman's uterus. In more severe cases, in-vitro fertilization (IVF) can be used, in which eggs are removed from the woman and fertilized with the man's sperm in a laboratory, with the resulting embryos being returned to the woman's uterus.
New England Journal of Medicine