Many women get urinary tract infections (i.e. UTI or bladder infection) from any physical contact with their genitals -- penile intercourse, oral intercourse, digital intercourse, sex toy use, masturbation, etc. To prevent this, some women drink lots of fluids before sex, and empty their bladders both before and after sexual activity (the acidity of the urine can help to kill some bacteria). Your partner washing before sex, especially under the hood of his penis if he's uncircumcised, couldn't hurt either to reduce the frequency of your infections.