Induction of ovulation monitored by ultrasound.

Eighty menstrual cycles were induced by the administration of human menopausal gonadotropin (hMG), and the induction of ovulation was evaluated by serial ultrasound scanning. Ovulation occurred in 57 of these cycles, and pregnancy occurred in 17 patients. No pregnancy occurred if the follicle size was below 15 mm at the time that human chorionic gonadotropin (hCG) was administered. A 15-mm follicle size is, therefore, regarded as a minimum size for a mature ovum. Multiple follicles were present in seven of the cycles where pregnancy occurred, but only two patients had multiple pregnancies. Ovarian hyperstimulation (OHS), which is characterized by cystic ovarian enlargement of greater than 5 cm after ovulation, was present in 25 cycles. This is a considerably higher incidence than previously documented, but since it is not possible to predict reliably its occurrence, and in no patients were the symptoms severe, it is considered an acceptable and inevitable sequela of ovulation induction. The present role of ultrasound is to establish whether the ovary responds to gonadotropin stimulation, to ensure that the follicle has reached a minimum size, to determine the number of preovulatory follicles to inform better the patient about the possibilities of multiple pregnancies, to establish that ovulation has occurred after administration of hCG, and to document the presence or absence of OHS.