The 20-year-old Californian woman is claiming she and 'Baby, Baby' singer Justin had sex backstage after his concert in LA last October, that he told her it was his 'first time' and she is demanding a paternity test and 'adequate support'.
The pop star's spokesperson has strongly denied the allegations, calling them 'malicious', 'defamatory' and 'demonstrably false'.
The 17-year-old superstar is known for his squeaky clean image and the news has stunned the world. The baby was born on July 6 and yesterday, October 31, Yeater filed a paternity lawsuit.
She has asked Justin Bieber to submit to a paternity test, and a claim 'to provide adequate support for my baby', for the sexual liaison which she allegedly lasted no longer than 30 seconds.
In a legal statement, sworn under penalty of perjury, Yeater told a California court that Bieber propositioned her on October 25 of last year, when she was 19 after his concert in LA.
According to US website Radar Online, Yeater told a judge: 'When I later realised I was pregnant with Justin Bieber's baby, I tried to contact him through his representatives but no one ever called me back.'
She added: 'On July 6 2011, I gave birth to a baby boy. That was exactly 36 weeks and two days after the sexual encounter with Justin Bieber.
'Based upon the timing as well as the fact there were no other possible men that I had sex with that could be the father of this baby, I believe that Justin Bieber is in fact the father of my baby.'
Bieber took to his Twitter page today telling his fans: 'So Im going to ignore the rumours...and focus on what is real an opportunity to help by doing what i love. Judge me on the music! Love yall!'
Bieber's spokesperson has denied the allegations, and told website Radar: 'While we haven't yet seen the lawsuit, it's sad that someone would fabricate malicious, defamatory, and demonstrably false claims.
'We will vigorously pursue all available legal remedies to defend and protect Justin against these allegations.'
Yeater wrote a detailed (maybe slightly too much!) statement about meeting her idol in papers submitted to a Los Angeles court.
She claims she was approached by a security guard while seated in the front row of the star's concert and asked if she wanted to meet the singer backstage.
She said: 'Immediately, it was obvious that we were mutually attracted to one another, and we began to kiss. Shortly thereafter, Justin Bieber suggested that I go with him to a private place where we could be alone.
'I agreed to go with him and on the walk to a private area, he told me he wanted to make love to me and this was going to be his first time.
'We went inside and immediately his personality changed drastically. He began touching me and repeatedly said he wanted to f*** the s*** out of me.
'At the time I asked him to put a condom on for protection, but he insisted that he did not want to. In his own words, he said that because it was his first time he wanted to feel everything.'
She is said to have described the intercourse as 'brief', lasting 'approximately 30 seconds'.
However, Yeater's claim that she had sex with the star when she was 19 and he was aged 16 would mean under California law that he was underage.
Yeater claims that after the encounter he refused to give her his phone number, and was 'not interested' in writing down her contact details.
She says that after learning she was pregnant she tried to get in touch with him via his representatives, but there was no response to her calls.
A court hearing is said to have been set for December 15.
Justin has been dating girlfriend Selena Gomez since the end of last year but the couple waited until the Oscars in March to make their first public debut together.
In February this year Justin, who is a Christian, spoke out about pre-marital sex in an interview with Rolling Stone magazine. He said: 'I don't think you should have sex with anyone unless you love them.'