UTIs are not STDs or STIs, but they can still be caused by sexual intercourse. Honeymoon Cystitis, for example, is a bladder infection that is often caused by sexual activity.
E. Coli is the type of bacteria that causes approximately 90% of uncomplicated UTIs. Sexual intercourse increases the risk that E. Coli or other bacteria could come into contact with the urethra, causing infection. This is particularly true for premenopausal women, as women's urethras tend to be shorter and located in closer proximity to the anus. The use of spermicides can also increase the risk of UTIs.
Urinating after engaging in sexual activity helps clear up the urinary tract and flush away bacteria, reducing the risk of UTIs.
Pregnant women are at a greater risk of contracting UTIs. As a pregnant woman's uterus expands, it may press on her bladder, making it harder for urine to enter the bladder and increasing the risk of infection.
Postmenopausal women are an at-risk population for different reasons. After menopause, lower estrogen levels, higher vaginal pH levels, and a decline in antimicrobial lactobacilli (the good kind, that is) all expose women to a higher risk of developing a UTI, according to the National Institutes of Health (NIH).
Infants are at risk of UTI, especially when they have dirty diapers or are improperly wiped from back to front. Good hydration and hygiene can help prevent urogenital infections in infants.
Men with enlarged prostates are also at greater risk for contracting a UTI, as a larger than normal prostate can block flow out of the bladder.
People with chronic conditions including diabetes are more likely to contract UTIs. People whose immune systems are compromised, including patients with HIV/AIDS, also experience an increased risk of UTI.