Transcript of WHO Press Release, April 2, 1996

A major breakthrough in the development of a new contraceptive for men is reported in the results of a four-continent, two-year clinical trial published by the World Health Organization (WHO) in the journal Fertility and Sterility (1). The method being developed relies on hormone injections to reduce the concentration of sperm in semen to either very low or undetectable levels. The overall contraceptive effectiveness achieved in this trial was 98.6%, which is comparable to the effectiveness of hormonal methods for women such as the oral contraceptive pill.

"The findings in the WHO study have brought us a step closer to developing a hormonal contraceptive for men," states Giuseppe Benagiano, Director of the WHO Special Programme of Research, Development and Research Training in Human Reproduction (HRP), which carried out the study.

The results of this trial are especially important because the development of new, safe, effective, reversible and acceptable contraceptive methods for men will expand the options available to couples who wish to plan their families. At present, the only contraceptive options available to men are the condom, withdrawal and vasectomy.

A total of 401 couples took part in the study which was carried out in 15 centers in 9 countries (Australia, 2; China, 4; France, 1; Hungary, 1; Singapore, 1; Sweden, 1; Thailand, 1; United Kingdom, 2; USA, 2). A requirement of the study was that the male partners were aged between 21 and 45 years and in a stable relationship in which both partners wanted contraception. Most of the men who volunteered to take part in the study did so because of their, or their partner's, dissatisfaction with other methods of contraception.

The treatment consisted of weekly injections of 200 mg of testosterone enanthate, a synthetic derivative of the male hormone, testosterone. The treatment regimen was known from previous studies to be effective in reducing sperm counts as well as safe and reversible. Efficacy of the treatment was measured in men who became either azoospermic (i.e., in whom sperm was not detectable in semen) or oligozoospermic (defined for the purposes of this study as men in whom sperm concentrations were lower than three million per milliliter of semen).

No pregnancies occurred in the partners of men rendered azoospermic by the treatment and only 4 pregnancies occurred in partners of men rendered oligozoospermic. The overall pregnancy rate (1.4 per 100 person years) is comparable with typical first year failure rates of modern reversible female contraceptive methods, including injectable and oral hormonal contraceptives, and is far superior to the currently available reversible male methods, condoms and withdrawal.

The average times taken to reach the required level of oligozoospermia or azoospermia were 68 and 100 days, respectively, from the first injection. When the treatment was stopped, the average times taken for the men to return to normal fertile levels of sperm production or to reach pretreatment levels of sperm production were 112 and 201 days, respectively. All of the 33 babies born to date to couples after they had taken part in the study were healthy and of normal weight.

The need for weekly injections, required by the use of testosterone enanthate, is considered a drawback. Therefore, WHO is studying longer-acting testosterone derivatives as well as combined hormonal preparations which will have the dual advantages of a longer interval, 3-4 months, between injections as well as a lower overall hormone dose. According to Dr. Benagiano, "The willingness of men to volunteer for the recently completed study, and other similar WHO-supported studies in the past, as well as their motivation and commitment to continue with the protocol of weekly injections, demonstrates the interest in - and demand for - a reversible male contraceptive of this type."

About the Special Programme

The Special Programme of Research, Development and Research Training in Human Reproduction (HRP) is cosponsored by the United Nations Development Programme (UNDP), the United Nations Population Fund (UNPFA), WHO and the World Bank, and is the main instrument within the United Nations system for reproductive health research. The Programme develops, tests and introduces new and improved methods of fertility regulation for women and men, conducts epidemiological and social science research on reproductive health, and helps developing countries to strengthen their resources for research in this area.


(1) World Health Organization, Task Force on Methods for the Regulation of Male Fertility. Contraceptive efficacy of testosterone-induced azoospermia and oligozoospermia in normal men. Fertility and Sterility, 1996; 65:821-829.



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