One factor may be that a woman's urethra is short, allowing bacteria quick access to the bladder. Also, a woman's urethral opening is near sources of bacteria from the anus and vagina. For many women, sexual intercourse seems to trigger an infection, although the reasons for this linkage are unclear. According to several studies, women who use a diaphragm are more likely to develop a UTI than women who use other forms of birth control. Recently, researchers found that women whose partners use a condom with spermicidal foam also tend to have growth of E. coli bacteria in the vagina.
Many women suffer from frequent UTIs.
Nearly 20 percent of women who have a UTI will have another, and 30 percent of those will have yet another. Usually, the latest infection stems from a strain or type of bacteria that is different from the infection before it, indicating a separate infection. A recent NIH-funded study has also shown that women with recurrent UTIs tend to have certain blood types. Some scientists speculate that women with these blood types are more prone to UTIs because the cells lining the vagina and urethra may allow bacteria to attach more easily. Further research will show whether this association is sound and proves useful in identifying women at high risk for UTIs.