Received January 29, 2022
Accepted July 31, 2022

To investigate the effect of endometriosis and its different stages over Intracytoplasmic Sperm Injection (ICSI) outcomes among infertile women without previous history of ovarian surgery. A total of 440 women enrolled in ICSI cycles were recruited and divided into two groups as endometriosis (n: 220) and control group (n: 220). Endometriosis patients without previous surgical treatment and with diagnostic laparoscopy were sub-stratified based on the stage of disease. Baseline characteristics of participants, clinical and laboratory parameters, ovarian reserve markers (AMH, FSH, and AFC), the number and quality of oocytes and embryos and fertilization rate were analyzed and compared between various severity grades of endometriosis and control group. Patients with advanced endometriosis (III/IV) had significantly fewer retrieved oocytes with small effect size (P < 0.001, η²=0.04), lower metaphase II oocytes (P < 0.001, η²=0.09) and fewer total numbers of embryos (P < 0.001, η²=0.11) compared with less severe disease or women with tubal factor infertility. The fertilization rate in women with severe endometriosis was similar to the control group and in those with minimal /mild endometriosis (p=0.187). Patients with severe endometriosis had a lower pregnancy rate compared to less severe diseases. Severe endometriosis negatively affects ovarian response and the quality of oocytes and embryos. However, the fertilization rate is not different between various stages of endometriosis.