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07/06/94

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Reversible male contraception possible by combining existing technology

STANFORD -- Combining vasectomy with existing technologies of cryogenic sperm preservation and artificial insemination could produce a reliable system for reversible male contraception.

Because this is the only new approach to male contraception likely to become available in the foreseeable future, the military services should set up a large-scale sperm cryopreservation program in order to create public confidence in the approach, and to work out its technical, legal and ethical aspects, a Stanford chemist says.

"Would it not be a dramatic gesture if the military were the vehicle whereby the responsibility for birth control would be more equitably shared by both males and females," says Carl Djerassi, professor of chemistry at Stanford University, widely known as the father of the birth control pill.

Djerassi and Stanley P. Leibo, research professor at the University of Guelph, propose this new approach to birth control in the July 7 issue of the British science journal Nature.

The absence of serious research and development in male contraception among the major pharmaceutical companies, combined with the fact that the process of developing, testing and regulatory approval of a truly novel male contraceptive requires 15 to 20 years, means that the prospect for a "male pill" is "dismal" even after the year 2010, the authors conclude.

Fortunately, recent developments have made it possible to achieve reversible male contraception through a combination of existing technologies, the scientists say.

Vasectomies are currently used almost exclusively by married men after they have had one or more children. Artificial insemination has become the primary method for treating male infertility. And the preservation of sperm at very low temperatures has been extensively used in animal husbandry, while clinical studies indicate that the "shelf life" of cryopreserved human sperm is decades, perhaps even centuries.

If young men could ensure their ability to father children by depositing their sperm in a sperm bank, they would be more likely to consider a vasectomy as a method of birth control, the authors say: "If successful reversal could be 'guaranteed,' young men who have never fathered children might become candidates for vasectomy, thus transforming it into a new method of reversible male contraception."

Unfortunately, attempts to make vasectomies mechanically reversible by inserting valves or removable plugs have so far proven unsuccessful. But recent techniques and data indicate that the previously considered but rejected option of collecting and preserving sperm prior to the operation make this combination of technologies the only new form of reliable male contraception that can be introduced within the next decade, Djerassi and Leibo argue.

Among the recent developments that they cite:

  • ______Development of highly effective artificial insemination techniques using fresh sperm that have cumulative pregnancy rates of about 75 percent, with rates only slightly lower for freeze- thawed sperm.
  • Evidence that cryopreserved sperm can be stored for decades, possibly even centuries, without damage or loss of potency.
  • New methods for typing and encoding semen samples at the time of freezing and thawing that virtually eliminate the problem of mistaken identity.

What is missing is not the science and technology required for such a system but adequate "confidence by a much wider circle of the medical community outside of reproductive specialists; by policy makers (including ethicists and legal experts); by entrepreneurs; by health insurers; and more importantly, by potential male users," Djerassi and Leibo say.

To instill this confidence, a large-scale, long-term sperm cryopreservation program is required, they argue. Initially, such a program would not be linked with vasectomies. But it would demonstrate the technical and operational reliability of the system, as well as help address the legal and ethical issues involved, and have a number of other important benefits as well:

  • Sperm that is collected would provide an invaluable resource for studies on male fertility and the Human Genome Project.
  • By subjecting samples to periodic laboratory analyses, scientists could learn important new information about the fecundity of preserved sperm. This material also could be used to rapidly verify new test procedures.
  • By distributing questionnaires to sperm donors every five years asking whether they have fathered children, and cross- checking the responses with the fertility of the stored sperm, scientists should be able to determine the accuracy of different tests of sperm fertility.

The logical place for such a demonstration program is the military, the scientists propose. This makes sense for several reasons, they say, including:

  • The military services are the source of the largest number of young men with detailed medical records that are readily available for follow-up examinations. With little difficulty and relatively minor expenditures, tens of thousands of volunteers could collect their own semen to be cryopreserved by the military.
  • A military sperm bank would serve as a form of genetic insurance against damage to sperm and, by allowing procreation after death, against death itself.

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