Morphological and functional relations of Graafian follicle growth to ovulation in women using ultrasonic, laparoscopic and biochemical measurements

The daily growth rates of ovarian follicles were recorded ultrasonically for five days until ovulation in 56 spontaneously ovulating women and related to endocrine and clinical parameters. Over the 5-day period, the average diameter of the follicle destined to ovulate increased from 12 to 23 mm, the second largest follicle from 6 to 12 mm, the third largest follicle from 5 to 9 mm and the fourth largest follicle from 4 to 8 mm. Similar but lesser growth rates occurred in the follicles in the contralateral ovary. Ovulation occurred within 24 hours of the luteinizing hormone (LH) peak, and the mean peak diameter of the ovulating follicle was 23.2 +/- 0.3 (SEM) mm, (range 18-29 mm) before ovulation, and subsequent luteal function was judged to be normal. Follicular growth was most closely correlated with increasing peripheral blood oestrogen levels. In 16 women who had a laparoscopy within 12 hours of the last ultrasound and following the LH peak, the mean diameter of the largest follicle as measured by ultrasound (23.6 +/- 0.4 mm) was similar to that measured at laparoscopy (22.8 +/- 0.04 mm) and estimated from the volume of follicular fluid aspirated (average 5.8 +/- 0.2 ml), 22.5 mm. The follicular fluid levels of progesterone were high on the day of the LH peak and blood progesterone levels had risen significantly indicating that luteinization of the dominant Graafian follicles had already occurred prior to ovulation. This study confirms that ultrasonic monitoring provides a reliable measure of follicular growth and allows studies correlating morphological changes with both normal and abnormal endocrine function of the human ovary.