Cervicovaginal scrapings from 675 women who had volunteered information about the time of their last coitus and their contraceptive and douching practices were stained with Papanicolaou stain and screened for spermatozoa. Generally, as the interval between coitus and preparation of the smears (postcoital interval) increased, the percentage of smears with spermatozoa and the mean number of spermatozoa per smear decreased, but the percentage of spermatozoa with tails did not change significantly. Spermatozoa were found irregularly after the seventh and rarely after the tenth postcoital day. Vaginal douching, pregnancy, use of oral contraceptives, coitus interruptus, condoms, and vasectomy were associated with reduced prevalence of spermatozoa in smears.
(JAMA 240:1875-1877, 1978)
Silverman EM, Silverman AG. Persistence of Spermatozoa in the Lower Genital Tracts of Women. JAMA. 1978;240(17):1875-1877. doi:10.1001/jama.1978.03290170057027