<P> A uterine contraction is a muscle contraction of the uterine smooth muscle . </P> <P> The uterus frequently contracts throughout the entire menstrual cycle, and these contractions have been termed endometrial waves or contractile waves . These appear to involve only the sub-endometrial layer of the myometrium . In the early follicular phase, these contractions occur once or twice per minute and last 10--15 seconds with a low amplitude of usually 30 mmHg . The frequency increases to 3--4 per minute towards ovulation . During the luteal phase, the frequency and amplitude decrease, possibly to facilitate any implantation . </P>

The term used to describe the contractions of the uterus