Bicuspid aortic valve(BAV) is a common congenital heart defect often associated with ascending aorta dilation. Current guidelines suggest surgical intervention for diameters ≥45mm in conjunction with surgical aortic valve replacement(SAVR). However, the optimal management of ascending aortas measuring 40-44mm remains controversial. Objectives: This study aims to evaluate the evolution of aortic diameter in patients with BAV and ascending aorta diameters between 40 and 44 mm undergoing AVR, assessing whether a conservative approach is justified. Methods: We conducted a retrospective observational study, analyzing 88 BAV patients who underwent SAVR between January 2012 and December 2018. Patients were divided into two groups based on preoperative ascending aorta diameters: <40 mm (Group 1, n=15) and ≥40 and <45 mm (Group 2, n=11). Follow-up of at least 5 years included aortic dilation rates, survival, and reoperation rates. Results: No significant differences were observed in aortic dilation between the two groups during follow-up, with overall annual dilation rates of 0.2±0.07mm/year. Survival rates were 86.3% for Group 1 and 81.9% for Group 2, with no reoperations required in either group. Conclusions: Patients with BAV and ascending aorta diameters of 40-44 mm do not require prophylactic aortic replacement during AVR, provided they undergo regular follow-up. These findings support current guidelines advocating conservative management for ascending aorta diameters in this range. However, in younger patients or those nearing the 45 mm threshold, surgical replacement may still be considered to preempt future complications.