Alterations in the normal vaginal microflora are associated with an increased risk for bacterial vaginosis, gonorrhea, human immunodeficiency virus infection and colonization with Escherichia coli, a critical step preceding urinary tract infections. Multiple factors can affect vaginal flora. Gupta and colleagues studied the effects of various contraceptive methods on the normal vaginal flora.

The prospective study included 331 women 18 to 40 years of age who presented at a student health service for contraceptive planning. Forms of contraception included oral contraceptive pills (103 women), a cervical cap (35 women), diaphragm-spermicide (75 women) and other spermicidal methods. Vaginal introital cultures were obtained at baseline and weekly for one month after the start of the new contraceptive method.

Women who used the cervical cap or diaphragm-spermicide were more likely to have abnormal vaginal Gram stains and a higher prevalence of E. coli colonization. The prevalence of E. coli increased significantly in the cervical cap group, from 17 percent at baseline to 40 percent at weeks 1 and 4. In the diaphragm-spermicide group, the prevalence of E. coli colonization increased from 15 percent at baseline to 48 percent at week 1, followed by a decline to 32 percent at week 4. In the oral contraceptive group, the prevalence of E. coli colonization decreased, from 22 percent at baseline to 12 percent at the fourth week. Oral contraceptive pills were not associated with a significant change in the vaginal flora. Use of spermicidal contraception within the preceding week was associated with an increase in the presence of abnormal bacteria in vaginal cultures.

The authors conclude that barrier methods of contraception alter vaginal flora. This change could increase the risk of urogenital infections. Women who develop clinical syndromes that are related to changes in vaginal flora may want to avoid barrier contraceptive methods and use oral contraceptive agents.