Hematuria can be from a non-serious (benign) cause: Menstruation; Vigorous exercise; Sexual activity; Kidney stones; Trauma; Infection (like a bladder infection. Bleeding after sex, known as postcoital bleeding, is common. It's usually Sex, especially vigorous sex, can cause small cuts or scrapes to the vagina. If you have vaginal dryness, you're at greater risk of developing a urinary tract infection. A blood vessel in the prostate or seminal vesicles can rupture during sex or Sustaining an injury to the urinary tract or genitals may cause blood to Sometimes, a minor injury — such as from vigorous sex — ruptures a. Blood in the urine can have a variety of causes. Inability to urinate; Passing blood clots through the urine; Pain during sex or heavy menstrual.