Background
Several studies have compared different distension media and analgesics to optimise the efficiency of outpatient hysteroscopy. However, studies comparing different uterine filling pressures are scarce.

Aim
The objective of this study was to evaluate and compare different uterine filling pressures during diagnostic outpatient hysteroscopy in an attempt to find the optimal pressure allowing adequate visualisation while minimising pain and increasing patient satisfaction.

Materials and Methods
This was a double‐blind randomised controlled trial. A total of 240 women who had diagnostic outpatient hysteroscopy were randomly divided into three equal groups: the uterine filling pressure was 30 mm Hg in group 1, 50 mm Hg in group 2 and 80 mm Hg in group 3. The primary outcome was adequate visualisation, and secondary outcomes were the proportion of completed procedures, pain perceived during the procedure, immediately after the procedure and 30 min later.

Results
Adequate visualisation was lower in group 1 (88.7% vs 97.5% and 98.7%; P = 0.009), but was not different between groups 2 and 3 (P > 0.999). The proportion of completed procedures was not different among the groups. There was a progressive increase in pain scores from the lower to the higher pressure groups during the procedure, immediately after the procedure and 30 min after completing the procedure.

Conclusion
Uterine filling pressure of 50 mm Hg was associated with better visualisation than 30 mm Hg and lower pain scores than that of 80 mmHg with no difference in the proportion of completed procedures.