Ultrasonic observation of the mechanism of human ovulation.

Nine subjects were studied by means of ultrasound to determine the precise time of ovulation and to document follicular changes immediately prior to, during, and after rupture. There were no demonstrable changes in the size of appearance of the follicle over a period of up to 7 hours prior to its rupture. In one of the four subjects in whom follicular collapse was witnessed, the follicle emptied completely within less than 1 minute. In two of the other three subjects, there was an initial rapid loss of fluid followed by a flower release of the remaining contents. This latter process took 7 minutes in the first patient and 35 minutes in the second patient. The slow phase of follicular collapse may well be an important aspect in the release of the ovum. The corpus hemorrhagicum was seen to develop within 1 hour of ovulation.