Background Bladder distension is thought to cause the uterine axis to become more aligned with the cervical canal. Among women undergoing assisted conception it has been demonstrated that having a full bladder facilitates the passage of an intrauterine catheter for embryo transfer.

Objective To determine if insertion of intrauterine contraceptive devices is easier in women who have a full bladder at the time of insertion.

Methods 200 women requesting intrauterine contraception with a pre-filled bladder were randomised to delayed emptying (after insertion; n=100) or immediate emptying (before insertion; n=100). Comparisons were made between doctors’ reported ease of insertion and women's pain scores.

Results There was no significant difference with reported ease of insertion between the groups. Doctors reported that insertions were either ‘very easy’ or ‘quite easy’ in 82% and 83% of women in the immediate and delayed emptying groups, respectively (95% CIs for difference −10% to +11%). There was no significant difference in reported pain scores, with mean pain scores (out of 10) of 3.8 and 4.4 in the delayed and immediate emptying groups, respectively.

Conclusions Bladder filling does not have a significant effect on ease of insertion of an intrauterine method of contraception. Insertion is mostly associated with low levels of discomfort, even in the presence of a full bladder.