Objective: To describe the clinical experience of our center with in vitro fertilization (IVF) in unstimulated cycles and to provide a comparison to stimulated cycles.
Design: Spontaneous ovulatory cycles were triggered with human chorionic gonadotropin in the midcycle, and 78 aspirations for IVF were performed, with the remainder of the IVF cycle proceeding in a standard manner.
Setting: The IVF program of the University of Southern California and the California Medical Center, Los Angeles, California.
Patients: Spontaneously ovulatory women (n = 46) with predominantly pelvic factor as their principal cause of infertility, under the age of 40, and no male factor.
Interventions: Human chorionic gonadotropin administration in midcycle, follicle aspiration, IVF, and embryo transfer.
Main outcome measures: Embryo implantation and pregnancy.
Results: Seventy-eight follicle aspirations resulted in 11 clinical (14%) and 9 ongoing (12%) pregnancies. The per embryo implantation rate was 13% clinical and 11% ongoing. There was no decrease in per cycle pregnancy rates (PRs) for up to three unstimulated cycles.
Conclusions: Unstimulated IVF is a viable alternative to stimulated cycles with PRs approximately one half those of stimulated cycles. It is reasonable to offer patients up to three cycles of unstimulated IVF without expecting a decrease in PRs.