Follicular and estradiol parameters that improve success with natural cycle in vitro fertilization.

Abstract To describe clinical thresholds for follicle size and estradiol levels to optimize success with natural cycle in vitro fertilization (NCIVF). Descriptive cohort of candidates for stimulated IVF, 15 mm was the optimal threshold for hCG trigger. Anti-Mullerian hormone and follicle-stimulating hormone levels did not predict success in NCIVF, and no statistical difference in clinical pregnancy rates between day 3 or day 5 embryo transfer was observed. NCIVF is an effective therapy for infertile patients regardless of their ovarian reserve. Cycle cancellation due to a premature LH surge can be reduced, without sacrificing success, by triggering smaller follicles above a threshold level of estradiol.