ObjectiveTo determine embryo quality (mean graduated embryo score [GES]) in infertile patients with endometriosis undergoing in vitro fertilization with embryo transfer (IVF-ET) compared with infertile patients without endometriosis.MethodsA case-control study was performed comparing 706 embryos (162 patients) divided into 2 groups: 472 embryos derived from patients without endometriosis (n= 109, infertile patients with tubal infertility) and 234 embryos from patients in the study group (n= 53, infertile patients with peritoneal endometriosis). All patients were subjected to IVF using an oestradiol-antagonist-recombinant follicle-stimulating hormone (FSH) protocol for ovarian stimulation. The mean GES was performed to evaluate all embryos at 3 points in time: 16 to 18 hours, 25 to 27 hours, and 64 to 67 hours. Embryo evaluation was performed according to the following parameters: fragmentation, nucleolar alignment, polar body apposition, blastomere number/morphology, and symmetry. The primary outcome measure was the mean GES score. We also compared fertilization, implantation, and pregnancy rates.ResultsAlthough the number of embryos transferred was greater in patients with endometriosis than in the control group (2.38 ± 0.66 versus 2.15 ± 0.54;p= 0.001), the mean GES was similar in both groups (71 ± 19.8 versus 71.9 ± 23.5;p= 0.881). Likewise, the fertilization rate was similar in all groups, being 61% in patients with endometriosis and 59% in the control group (p= 0.511). No significant differences were observed in the implantation (21% versus 22%; [p= 0.989]) and pregnancy rates (26.4% versus 28.4%;p= 0.989).ConclusionEmbryo quality measured by the mean GES was not influenced by peritoneal endometriosis. Likewise, the evaluated reproductive outcomes were similar between infertile patients with and without endometriosis.