Genital tract infections associated with the intrauterine contraceptive device can be reduced by inserting the threads into the uterine cavity.

Objective: To study the influence of the position of the threads of an intrauterine contraceptive device (IUCD) on the development of genital tract infection.

Design: A multicentre randomized controlled trial.

Subjects: Women requesting an IUCD.

Interventions: The women were randomized to be fitted with an IUCD either with the threads contained in the uterine cavity (threads-up group) (n = 208) or passing through the cervix to the vagina in the usual way (threads-down group) (n = 237). Multiple centre study with follow-up at three months, 1 and 2 years. At the final visit 'missing' threads were retrieved using a disposable instrument (Retrievette).

Main Outcome Measures: The occurrence of infection in the lower or upper genital tract.

Results: 63 women in the threads-up group and 78 in the threads-down groups dropped out. Previous gynaecological infection was reported by 21 and 48 women in the threads-up and threads-down group, respectively (odds ratio 0.44, 95% CI 0.24 to 0.79), 21 and 53 subjects had signs of infection at gynaecological examination (odds ratio 0.39, 95% CI 0.21 to 0.69) and a wet-smear was pathological in 33 and 79 (odds ratio 0.38, 95% CI 0.23 to 0.61). In the threads-up group the vaginal pH was also lower at the final check up after 2 years. Spontaneous descent of the threads occurred in 11% of the threads-up group and in six women in the threads-down group the threads were in the cervix. In 93 women the threads were easily retrieved by means of the Retrievette, four women insisted on the threads remaining in the uterus and in 18 thread removal was performed under local or general anaesthesia.

Conclusions: Infectious complications in women using an IUCD are more frequent if the threads lead from the uterine cavity to the vagina. This problem can be reduced by inserting the threads so that they remain entirely within the uterine cavity, a feasible procedure now that an effective instrument for IUCD thread retrieval is available.