Recurrent infections (often defined as two or more in six months, or three or more in a year) have several contributing factors: sexual activity, use of spermicides or a diaphragm, low oestrogen after menopause causing tissue changes, not emptying the bladder fully, constipation, dehydration, and individual anatomy. Genetics and bacteria that persist in the bladder can also play a role.
Prevention measures that may help include staying well hydrated, urinating after sex, not delaying when you need to go, and managing constipation. For postmenopausal women, vaginal oestrogen can reduce recurrences, and in some cases doctors consider preventive antibiotic strategies.
Because repeated infections can occasionally point to an underlying issue, it is worth a proper assessment. A clinician may arrange urine testing and, in some cases, further investigation, then tailor a prevention plan to your circumstances.