Different sizes of uterine septum between infertile women and patients with abortions may have a clinical relevance in reproductive performance after surgery. This study aimed to assess if the fecundity of women after surgical correction of the uterine septum is associated with septum size.A retrospective, single-center, cohort study was conducted in Peking Union Medical College Hospital using patients aged between 21 and 37 years. Hysteroscopic metroplasty was performed on 121 patients with a uterine septum. The septum size was assessed by ultrasonography and hysteroscopy. The subjects were divided into 3 groups: Group A consisted of 35 women with complete uterine septum (mean ± standard deviation (SD) age 28.29 ± 3.53; group B consisted of 48 women with uterine septum >2.5 cm (mean ± SD age 28.85 ± 3.63); and group C consisted of 48 women with uterine septum ≤2.5 cm (mean ± SD age 28.79 ± 3.74). Age and body mass index (BMI) were not significantly different among the 3 groups.No serious hysteroscopic complications occurred. However, uterine septa were observed in 4 cases after surgery and 6 cases of intrauterine adhesions were observed after long-term follow-up. The abortion rate decreased, and term delivery rate increased significantly in the 3 groups after hysteroscopic metroplasty. The infertility rate was significantly lower in group C after surgery. However, no significant difference was observed in the infertility rate between groups A and B. The recurrent abortion rate was significantly lower in group A than in groups B and C before surgery. After surgery, the infertility rate was significantly higher in group A than in group B (28.57% and 10.53%, respectively; P = .048). After at least 12-months of follow-up, the pregnancy rate in group A was significantly lower than that in group C (71.43% and 89.47%, respectively; P = .048).Uterine septum resection improves obstetrical outcomes. After surgery, the infertility rate was significantly higher in patients with complete uterine septum than in those with a large partial uterine septum, and the pregnancy rate in patients with complete uterine septum was lower than that in the patients with a small partial uterine septum.