ABSTRACT
<p><b>BACKGROUND</b>Endometriosis affects natural fertility through various approaches, and in vitro fertilization (IVF) is a good treatment. But the IVF result of endometriosis patients is still under debate. We investigated the effect of endometriosis on IVF by analyzing the data from a single reproductive center.</p><p><b>METHODS</b>A retrospective, database-searched cohort study was performed. Relevant information was collected from the electronic records of women who underwent IVF/intracytoplasmic sperm injection between January 2006 and December 2010 in the Assisted Reproductive Unit of Sir Run Run Shaw Hospital. Patients with endometriosis were enrolled the study group. The rest of the women formed the control group. The main outcome was the clinical pregnancy rate. Secondary outcomes were oocytes retrieved number, fertilization rate, high-quality embryo rate, number of high-quality embryo for embryo transplantation, and implantation embryo/high-quality embryo ratio (IE/HQE ratio). Comparisons were performed by the c(2)-test and independent t-test.</p><p><b>RESULTS</b>The endometriosis group (n = 177) had a markedly lower oocytes retrieved number, fertilization rate, implantation rate, and clinical pregnancy rate (7.6 ± 5.1, 63.6%, 27.7%, and 45.2%, respectively) compared with the non-endometriosis group (n = 4267; 11.8 ± 7.3, 68.4%, 36.2%, and 55.2%, respectively). Stratified analysis showed that this difference was found in the subgroup younger than 35-years old, while only fertilization rate and implantation rate were different in the elder subgroup. The ratio of high-quality embryos transferred is lower in endometriosis group (53.7% vs. 71.8%, P < 0.05), but there is no difference in IE/HQE ratio between two groups. There is no significant difference in fertilization rate, implantation rate, and clinical pregnancy rate between mild and severe endometriosis patients.</p><p><b>CONCLUSIONS</b>Endometriosis patients suffer a decreasing IVF pregnancy rates mainly caused by reducing oocytes number and fertilization rate, regardless of the severity of the disease. Appropriate intracytoplasmic sperm injection manipulation might improve the outcomes of IVF.</p>