Antral follicle responsiveness to follicle-stimulating hormone administration assessed by the Follicular Output RaTe (FORT) may predict in vitro fertilization-embryo transfer outcome

Looking for a qualitative marker of ovarian function, we aimed to verify whether responsiveness of antral follicles to FSH administration, as reflected by the Follicular Output RaTe (FORT), is related to their reproductive competence. METHODS We studied 322 IVF-ET candidates aged 25–43 years who underwent controlled ovarian hyperstimulation with similar initial FSH doses. Antral follicle (3–8 mm) count (AFC) and pre-ovulatory follicle (16–22 mm) count (PFC) were performed, respectively, at the achievement of pituitary suppression (before FSH treatment) and on the day of hCG administration. The FORT was calculated by PFC × 100/AFC. FORT groups were set according to tercile values: low (58%; n= 97). RESULTS The average FORT was 50.6% (range, 16.7–100.0%). Clinical pregnancy rates per oocyte retrieval increased progressively from the low to the high FORT groups (33.3, 51.2 and 55.7%, respectively, P< 0.003) and such a relationship assessed by logistic regression was independent of the confounding covariates, women's ages, AFC and PFC. CONCLUSIONS The observed relationship between IVF-ET outcome and the percentage of antral follicles that effectively respond to FSH administration reaching pre-ovulatory maturation suggests that FORT may be a qualitative reflector of ovarian follicular competence. Further studies with broader inclusion criteria and more personalized protocols are needed to validate these results.