The dynamics of rapid sperm transport through the female genital tract: evidence from vaginal sonography of uterine peristalsis and hysterosalpingoscintigraphy.

Vaginal ultrasonography of uterine peristalsis during the follicular phase of the menstrual cycle demonstrates an increasing frequency and intensity of subendometrial and myometrial peristaltic waves as the follicular phase progresses. During this time the numbers of contraction waves with a fundo-cervical direction decrease considerably in favour of waves of contraction with a cervico-fundal direction. There is evidence that rapid sperm transport through the female genital tract is passive and is provided by these uterine contractions. Using hysterosalpingoscintigraphy, rapid sperm transport was studied by placing technetium-labelled albumin macrospheres of sperm size at the external os of the uterine cervix and following their path through the female genital tract. Ascension of the macrospheres occurred immediately following deposition at the external os of the cervix. As early as 1 min thereafter, the macrospheres had reached the intramural and isthmical part of the tube. Quantitatively, the extent of ascension increased with progression of the follicular phase. While only a few macrospheres entered the uterine cavity and even fewer the tubes during the early follicular phase, the proportion of macrospheres that entered the uterine cavity increased dramatically during the mid-follicular phase despite continuing limited entry into the tube. During the late follicular phase there was considerable ascension of the macrospheres which was directed preferentially into the tube ipsilateral to the dominant follicle. These data indicate that rapid transport of the spermatozoa through the female genital tract is under the endocrine control of the dominant follicle, ensuring the preferential accumulation of spermatozoa at the site of fertilization.