Background T-shaped intrauterine devices (IUDs) with a copper surface area of 380 mm² and copper bands on the transverse arms are the most effective types of copper-containing IUDs. A small-sized ‘gold standard’ IUD is available but there has been little research to compare the effects of this small-sized IUD to its standard-sized counterpart.

Aim To determine discontinuation rates and reasons for discontinuation at 1 year of the small-sized Mini TT380 Slimline IUD compared with the standard-sized TT380 Slimline.

Methods The clinical records of women fitted with Mini TT380 Slimline (‘mini’) IUDs were compared with those of women fitted with standard-sized TT380 Slimline (‘standard’) IUDs over a 3-year period (2013–2016).

Results Clinical records were available for 67 women fitted with a mini IUD (mean age 23 years, 64% nulliparous) and 63 women fitted with a standard IUD (mean age 25 years, 39% nulliparous). At 1 year, twice as many standard IUD users (32%, n=20) had discontinued their IUD use compared with mini IUD users (15%, n=10). Complaints of pain and bleeding were more than double (70%, n=14) in those women who discontinued standard IUD use compared with those who discontinued using the mini IUD (30%, n=3). These differences were statistically significant and were unrelated to parity.

Conclusions More women using a standard-sized ‘gold standard’ IUD rather than its smaller counterpart complained of pain and bleeding, leading to higher discontinuation at 1 year. More research on the association between size and discontinuation of these IUDs is needed.