CONTINUOUS MEASUREMENT BY RADIO-TELEMETRY OF VAGINAL pH DURING

Summary. The use of the pH-pill has allowed continuous monitoring of vaginal pH during human coitus. In the case of a couple of normal fertility, there was an immediate buffering by seminal plasma so that the vaginal pH changed in 8 sec from pH 4\m=.\3to pH 7\m=.\2.In the case of a couple of low (male) fertility, the immediate effect of the arrival of semen in the vagina was a change from pH 3\m=.\5to pH 5\m=.\5.A similarly small change in pH occurred when the seminal volume of a fertile male subject had been depleted, by repeated ejaculation, to 1 \m=.\5ml. At this pH(5\m=.\5),spermatozoa are generally immobilized. It has been possible to alter normal fertility, as judged by postcoital tests for sperm motility, by the introduction of a pH 3\m=.\6buffer solution into the vagina before coitus. In this latter experiment, the vaginal pH immediately after ejaculation was 5\m=.\0and, after 2 hr, had reached pH 5\m=.\4. These results in vivo suggest that the vagina is not the hostile environ-ment hitherto imagined, since the normal ejaculate readily overcomes the vaginal acidity by its powerful buffering action. Low seminal volume, with or without a concomitantly low sperm count, and artificial changes in vaginal environment by buffer solutions may affect fertility