What causes frequent urinary tract infections?

Two common causes. Frequent utis in adults especially in women are often related to sexual activities and personal susceptibility.
Many causes. 1) going to sleep with a full bladder after sex, instead of urinating first 2) toilet hygiene: not wiping front to back + trapping urine in vagina with voiding by keeping thighs togther rather than spreading them apart 3) baths and bubble-bath rather thjan showering 4) constipation 5) wearing thongs 6) witholding and long intervaks between urination 7) pregnancy 8) poor diet 9) morbid obesity.