The 24-year-old beauty representing Pennsylvania in this weekend's Miss Usa pageant has revealed her father is a rapist.

Pretty Valerie Gatto was conceived when her mother was sexually assaulted at knifepoint, at the age of 19.

Her mum wasn't able to identify her attacker, who forced himself on her from behind on a dark street, but she never attempted to lie to her daughter about her 'dad'.

Gatto tells, "She told me a very bad man hurt me, but God gave me you."

Now an advocate for sexual assault awareness, the pageant queen insists she was put on the earth "for a reason", adding, "(I'm here) to give hope that everything is possible and you can't let your circumstances define your life.

"I hope to show others how to be proactive, what to do, to be present, to be aware of your surroundings. It's so awesome to see their responses. They say it changes their life."

The Miss Usa pageant takes place in Baton Rouge, Louisiana, on Sunday (08Jun14).