Ovarian sensitivity index can be used as a more sensitive indicator than follicular output rate to predict IVF/ICSI outcomes in patients of normal expected ovarian response stimulated with GnRH antagonist protocol.

This retrospective study was performed to investigate the predictive power of the Ovarian Sensitivity Index (OSI) for IVF/ICSI outcomes in infertile patients who were of normal expected ovarian response. A total of 912 infertile patients who underwent GnRH antagonist protocol between January 2017 to August 2019 at the Medical Center for Human Reproduction, Beijing Chao-Yang Hospital were included. All patients completed the full oocyte retrieval cycle and either had a live birth or had no embryos left. OSI was significantly lower in patients with a live birth (196.0 ± 120.4 in the live birth group vs 276.4 ± 235.7 in the non-live birth group, p < 0.001) while follicular output rate (FORT, defined as the ratio of pre-ovulatory follicle count on hCG day x 100/small antral follicle count at baseline) showed no significant difference. Patients were divided into low, average and high OSI groups and analysed in tertiles. From the low to the high OSI group, the cumulative live birth rate (CLBR) decreased dramatically (72.7 vs 67.2 vs 54.8%, p < 0.001). Multivariate regression analysis showed that OSI was an independent factor affecting CLBR (OR: 0.996, 95%CI: 0.995-0.998, p < 0.001) in our study population. In conclusion, OSI can be used as an independent indicator to distinguish fecundity in infertile patients with normal expected ovarian response and is probably more sensitive than FORT.