Failure of human oocyte release at ovulation

Among 150 patients admitted for ovum aspiration, in vitro fertilization, and embryo transfer in Perth, Western Australia, 14 were found to have had at least one ovulated follicle at the time of laparoscopy. Based upon ultrasound estimation of follicle diameter 24 hours previously, ovulation occurred in 6 of 22 follicles less than 1.7 cm in mean diameter and in 16 of 19 follicles greater than 1.7 cm in mean diameter. When the ruptured follicles were flushed with heparinized fertilization medium, oocytes were collected in 13 of the 22 dispersed follicles. Twelve oocytes developed pronuclei 16 hours after the addition of spermatozoa, and 11 cleaved to the 4-cell stage within 44 hours of insemination. Oocytes were recovered from 6 of 11 patients stimulated with clomiphene alone and from all 3 patients stimulated with clomiphene supplemented with human menopausal gonadotropin. These observations suggest that oocyte release and follicle rupture are not necessarily synonymous events and that the incidence of retained oocytes in ovulated follicles following stimulation with clomiphene or clomiphene plus human menopausal gonadotropin could be on the order of 60%.