Abstract: Objective:To investigate the effect of uterine junctional zone (JZ) detected by transvaginal three-dimensional ultrasound (3D-TVUS) on the pregnancy rate of in vitro fertilization and embryo transfer (IVF-ET). Method:The JZ of 128 infertile patients receiving IVF-ET were measured by 3D-TVUS on the day of hCG injection. The data of JZs relating to the shape and thickness including the maximum thickness (d_JZmax), the minimum thickness (d_JZmin) and their difference (Δd_JZmax-min) on the coronal section of uterus obtained by 3D-TVUS were evaluated respectively and then the differentiations were compared between pregnancy and non-pregancy groups. Results:The clinical pregnancy rate was 56.25% in 128 cases. Compared with pregnancy group, d_JZmax and Δd_JZmax-min in non-pregnancy group increased significantly (P<0.01). When the cut-off value of d_JZmax was 6.75 mm, the diagnostic sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 94.4%, 62.5%, 72%, 92%, and 94%, respectively. And when the cut-off value of Δd_JZmax-min was 3.75 mm, the diagnostic sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 91.7%, 69.6%, 75%, 89%, and 92%, respectively. The failure rate of IVF-ET with JZ morphological abnormality was 5.42 times higher than that of the normal (RO=5.42, and the 95% confidence interval is 2.45-11.97). Conclusion:JZ can be used as a routine predictor of IVF-ET outcome, and JZ abnormality may lead to IVF-ET failure.