Predictors of ovarian response: progress towards individualized treatment in ovulation induction and ovarian stimulation

Ovarian stimulation is applied in the clinic to restore mono-ovulatory cycles in anovulatory women (ovulation induction) or to induce the development of multiple dominant follicles for assisted reproduction. Ovarian response is the endocrine and follicular reaction of the ovaries to stimulation. Achieving an appropriate ovarian response to anti-estrogens or exogenous gonadotrophins is central to ovulation induction and ovarian stimulation protocols. However, achieving an adequate response, without cycle cancellation or adverse events related to under- or over-stimulation, is complicated by high intra- and inter-individual variability. To predict each patient's ovarian response to medication for ovarian stimulation and to individualize the starting dose of exogenous gonadotrophin or the need for exogenous luteinizing hormone, various clinical, endocrine, ovarian ultrasonographic and genetic characteristics have been explored. Some of these features have been incorporated into prediction models. In this review, the methodology behind predictive factors and prediction models and their potential clinical applicability across ovulation induction and ovarian stimulation are explored.