Textbook Definition of Male Fertility Questioned
Study finds flaws, suggests changes in rules
WEDNESDAY, Nov. 7, 2001 (HealthDayNews) -- The textbook rules for assessing a man's ability to father a child aren't quite right, says a new study that suggests changes in the way a sperm sample is classified as normal or abnormal.
About one in six couples have difficulty achieving pregnancy, and male infertility is the problem perhaps 40 percent of the time. The current standard for estimating the fertility of a sperm sample, set by the World Health Organization (WHO) is based primarily on sperm count and motility -- the ability of sperm to move about -- and delivers a yes or no answer: A man is either fertile or infertile.
But the new study finds that the most important influence on fertility is a third factor, morphology -- whether sperm look normal under a microscope. And it says that the determination of fertility is not clear-cut in a large percentage of cases.
"In our analysis, there is an indeterminate zone," says Dr. David Guzick, chairman of obstetrics and gynecology at the University of Rochester Medical Center and lead author of a report in the Nov. 8 issue of The New England Journal of Medicine. "We allow for a wide range, which will be helpful in counseling and might save men from unnecessary treatment."
Guzick says he and his colleagues began to question the WHO standards during earlier studies. "So we went back to the basic manual and found that the reference values did not have an empirical basis. They were not based on data about fertile and infertile patients but on a number of extrapolations and opinions."
To come up with new standards, the researchers compared semen samples from 765 men in infertile couples with 696 samples from men who had fathered children. The numbers they came up with differed from those based on the WHO rules.
The WHO criteria say that fertile semen contains 20 million sperm per milliliter, with at least 50 percent motility. The Rochester study found that men are most likely to be fertile if their semen had more than 48 million sperm per milliliter with more than 63 percent motility.
But those readings are not definitive, Guzick says. There is a gray zone in which men have borderline fertility. That middle zone lies above the readings at which men are more likely to be infertile -- fewer than 13.5 million sperm per milliliter, and less than 32 percent motility, with fewer than 9 percent of sperm with a normal shape.
Guzick says morphology was the most important factor in the study, and it is the most difficult to measure. "For the other two, if you have a computer, you put the sample in and get your count and motility. But morphology is a separate part of the evaluation. It requires someone trained in the procedure, and it is expensive."
Using the new measures of sperm count and motility and adding morphology "will help to make counseling and appropriate treatment more effective than ever before," he says.
"This study confirms what most of us in the field have suspected for a long time," says Dr. Marc Goldstein, director of the Cornell Institute for Reproductive Medicine in New York City. "We have believed that morphology is important, and this is one of the best studies about that point."
The finding that the WHO standards are imperfect comes as no surprise, Goldstein says. "Most of us have seen individuals who are abnormal by WHO standards and have no problem, and vice versa," he says.
But even careful evaluation of morphology -- something his center does in every case -- does not always provide definitive information because there can be other problems, he says. "A man can have an allergy to his own sperm. The sperm can be coated with antibodies, so that it is attacked by the immune system, so the couple experiences infertility. But it is still worthwhile having morphology evaluated," Goldstein says.
What To Do
A couple trying to achieve a pregnancy should ask about the tests and criteria used to assess fertility of both the man and the woman.