Contractility of the nonpregnant uterus: the follicular phase.

Recent renewed interest in uterine contractility stems from the possibility of directly visualizing uterine contractility on images generated by high-resolution ultrasound probes. During the menstrual cycle, three typical patterns of uterine contractility have been recognized. During the luteofollicular transition and early follicular phase (menses), the contractile event involves all layers of the myometrium and exerts antegrade (from fundus to cervix) expulsive forces. Characteristically, uterine contractions are often perceived by women at the time of menses, sometimes reaching the level of painful cramps (dysmenorrhea). In the late follicular phase, uterine contractility involves only the subendometrial layers of the myometrium and is never perceived by women. The primary function of uterine contractility in the late follicular phase is to facilitate the retrograde (cervix to fundus) transport of sperm towards the distal end of the fallopian tubes where fertilization normally takes place. Finally, the uterus reaches a stage of quiescence after ovulation (under the influence of progesterone) that characterizes the major part of the luteal phase. The present review summarizes our understanding of the physiological role of uterine contractility during the follicular phase and the possible implications in pathological circumstances such as endometriosis and dysmenorrhea.