Mieusset, R. and Bujan, L. (1994) The potential of mild testicular heating as a safe, effective and reversible contraceptive method for men. International Journal of Andrology, 17, 186-191.

  Centre de Sterilite Masculine and CECOS Midi-Pyrenees, Hospital La Grave, Toulouse, France

Summary:
  A Preliminary assessment of the contraceptive efficacy of a daily mild increase (1-2C) in testicular temperature during waking hours is reported in nine couples using two techniques of non-surgical fixation of the testes close to the inguinal canal. With technique 1, immobilization was achieved by passing the penis and the empty scrotum through a hole made in close-fitting underwear; there was one pregnancy, from a man who stopped the heating after 7 weeks, for 42 cycles of exposure in three couples. With technique 2, immobilization was achieved by adding a ring of soft material surrounding the hole in the underwear; there was no pregnancy for 117 cycles of exposure in six couples. Reversibility and safety were assessed. These preliminary results suggest that a daily mild increase in testicular temperature could be a potential contraceptive method for men.

Discussion:
  Regardless of the technique used, a contraceptive method is required to fulfill four characteristics: (1) safety for the user and his partner, (2) reversibility of the contraceptive effect, (3) high efficacy as a means of birth control, and (4) acceptability to the user.
  (1) Safety. No complaint or pain of any kind was reported by any of the men in our study, and none of the men involved in the present study dropped out because of discomfort or any compliance problem. Libido was never depressed and sexual rhythm was unmodified. No modification was observed in the clinical examinations performed during and after the heating period. However, as testicular volumes were not measured but evaluated subjectively, small modifications cannot be excluded completely.
  (2) Reversibility. After heating was stopped, sperm counts in all of the men involved in the present study recovered to their pre-heating values, as was reported in part in previous studies (Mieusset et al., 1985, 1987a). Fertility was also restored as indicated by the occurrence of pregnancies for the three men who used technique 1. Moreover, three other men using the same heating technique in a preliminary study (Mieusset et al., 1991) have fathered a child without any problem within 2-4 years after the end of a 6-36-month period of exposure to heat. There were no miscarriages and no pathologies in the five babies, who are now 3-6 years of age.
  (3) Efficacy. Pearl rates were 28.6 and 0.0 per 100 years for heating techniques 1 and 2 respectively. The greater suppression of sperm output achieved by technique 2, in which the maximum motile sperm concentration never rose above 1.6 million/mL (Table 1), appeared to assure better contraceptive efficacy than did technique 1.
  (4) Acceptability. The present study was designed as an experimental protocol to evaluate the potential contraceptive efficacy of mild testicular heating. Thus, mild testicular heating was never really suggested to be used as a contraceptive method by men asking for male contraception, since before the results of the study the real contraceptive efficacy of such a method was unknown. As regards the volunteers involved in the present study, which was supposed to last for between 6 and 12 months, the mean heating time was 17 months (range 6-49 months), which could indicate a good compliance and that the techniques were reasonably comfortable. Acceptability of mild testicular heating as a potential contraceptive method for men must be evaluated in the general population.