Identification of follicles with fertilizable oocytes by sequential ultrasound measurements during follicular development.

Patients undergoing ovulation induction for in vitro fertilization and embryo transfer (IVF-ET) were monitored daily with serum estradiol-17 beta (E2) and ultrasound. The location of each individual follicle was established by taking ultrasound images through serial sections of the ovary. The diameter of each follicle and the volume of its follicular wall (FW) were determined from ultrasound images using a computer-controlled image analyzer. A total of 44 follicles from nine patients was studied, with an overall fertilization rate of 46% In all patients, serum E2 levels increased prior to human chorionic gonadotropin (hCG). Whereas changes in either the average diameter or the volume of the entire follicle did not identify follicles with fertilizable oocytes, FW volume measurements were predictive. Prior to hCG, FW volume increased 24 +/- 8%/day in follicles with fertilizable oocytes but decreased 3 +/- 6%/day in follicles with nonfertilizable oocytes (P less than 0.05). Three major patterns of follicular development were observed for follicles with nonfertilizable oocytes: slow growing (less than 20% increase in FW volume), nongrowing (no change in the FW volume), and "degenerating" (a decrease in the FW volume), suggesting that these follicles are "postmature." These data demonstrate that FW volume measurements made from sequential ultrasound images provide an accurate method to identify those follicles that contain fertilizable oocytes.