Why does my girlfriend urinate uncontrollably when she climaxes?

Orgasm and leaking: Some women have the ability to " ejaculate" with orgasm. In these women it is believed to be a prostatic like fluid produced in cells near the urethra. Or orgasm can cause spasming of the pelvic floor, bladder, urethra, uterus, rectum. Spasm of the bladder could cause leakage of urine with orgasm. Another possibility is a weakness of the urethra or bladder prolapse can cause leakage with sex.

Voiding reflex: Is triggered by climax in some women, this can cause uncontrolled urination. Some men & women find this very exiting.