Endometriosis as a cause of reduced IVF success rates: guilty beyond reasonable doubt?

Endometriosis is a chronic inflammatory disease that affects around 10% of women of reproductive age and is frequently associated with infertility. Despite its high prevalence in assisted reproductive technology (ART) cycles, the exact mechanisms by which endometriosis may impair in vitro fertilization (IVF) outcomes remain under debate. This integrative narrative review critically examines the evidence on how endometriosis may affect oocyte quality and competence, ovarian reserve, and endometrial receptivity. While several studies have suggested molecular and cellular alterations in the follicular microenvironment and endometrial environment, population-based registry analyses have reported conflicting results regarding their clinical impact. Instead, the most reproducible negative impact appears to be a reduction in the number of oocytes retrieved, particularly in cases involving endometriomas or after ovarian surgery. Similarly, while endometrial alterations have been observed in women with endometriosis, large registry-based studies of donor oocyte cycles suggest only a marginal impairment of endometrial receptivity, if any. Taken together, reasonable doubt remains regarding the extent to which endometriosis influences fertility outcomes in IVF cycles.