Results of a pilot study of the time to azoospermia after vasectomy in Mexico City.

In a joint pilot study by Family Health International (FHI), AVSC International, and the Instituto Mexicano del Seguro Social (IMSS), information was gathered on the determinants of azoospermia following vasectomy on 38 healthy men who chose vasectomy for contraception. The time and number of ejaculations associated with loss of sperm motility and loss of sperm eosin vital staining were also evaluated. "Azoospermia" was defined on the basis of two consecutive azoospermic semen samples collected at least 3 days apart. The single decrement life table method was used to calculate weekly gross cumulative life table rates for the time to azoospermia, zero motility, and zero viability. The Kaplan-Meier method was used to calculate the product-limit estimates of the cumulative rates for the total number of ejaculations to azoospermia, 0% motility and 0% viability. The median time to azoospermia was 10 weeks and at the end of week 20, the life table rate (+/- standard error) was 93.0 (+/- 6.30) weeks/100 men. The median number of ejaculations to azoospermia was between 25 and 30, and the cumulative rate (+/- standard error) at 60 ejaculations reached 94.5 (+/- 5.16)/100 men.