No significant difference could be shown in the development of abnormal vaginal flora in women fitted with an IUCD compared with IUS users, in a study from the UK.

A total of 172 women requesting IUCD or IUS contraception were recruited to the study from contraceptive clinics between August 2000 and April 2003. In all, 78 women had a copper IUCD inserted and 94 had a progesterone-incorporated IUS. The women were assessed before and twice after fitting, using high vaginal swabs and Ison-Hay criteria for grading vaginal flora.

Patients were significantly more likely to have developed an abnormal vaginal discharge 4-6 weeks after insertion of an IUCD compared with an IUS; this was not significant at the six-month follow-up visit. Most of the women with abnormal discharge had normal vaginal flora. Although women who had a copper IUCD inserted were more likely to have bacterial vaginosis at both follow-up visits, the small numbers meant there was not enough power to determine if there were significant differences.

Bacterial vaginosis is known to be more common in women using IUCD contraception but there is conflicting evidence around the influence of hormones on vaginal flora and hence bacterial vaginosis.

Despite the lack of evidence supporting the notion of abnormal vaginal discharge, it might be important to include this possibility in discussions with women who wish to use either form of intrauterine contraception.