Do you not know the Catholic teaching on the subject??  

The Ethical and Religious Directives are very helpful - health care providers are certainly encouraged to provide treatment to prevent possible venereal disease and pregnancy. 

"36. Compassionate and understanding care should be given to a person who is the victim of sexual assault. Health care providers should cooperate with law enforcement officials and offer the person psychological and spiritual support as well as accurate medical information. A female who has been raped should be able to defend herself against a potential conception from the sexual assault. If, after appropriate testing, there is no evidence that conception has occurred already, she may be treated with medications that would prevent ovulation, sperm capacitation, or fertilization."

This article may help you if you are serious about understanding:
http://www.catholiceducation.org/en/culture/catholic-contributions/ethical-treatment-after-rape.html