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Nicole Richie has further fuelled pregnancy rumours by abstaining from alcohol at a showbiz party.

The 26-year-old - who allegedly received test results confirming she is pregnant two weeks ago - attended the Yves Saint Laurent Centre Dance Arts party at the Beverly Hills Hotel with boyfriend Joel Madden.

A source told the New York Daily News newspaper: "Nicole had everyone whispering when she declined alcohol."

The Simple Life star - renowned for her skinny frame - first sparked rumours after being photographed with an apparent baby bump.

A source told Life and Style Weekly magazine last week: "Nicole recently underwent a series of tests, including blood and urine screenings, which confirmed she is pregnant."

Nicole was photographed outside a reproductive clinic last month - just days after her alcohol-fuelled Memorial Day barbecue.

She is said to be going on a special diet for the sake of her unborn child.

An insider said: "Nicole's determined to get healthy for her own sake and the baby's."

The star's representative has refused to comment on the pregnancy reports.

Nicole is said to be engaged to Good Charlotte frontman Joel.

Meanwhile, Richie today won a more than two-week postponement of her trial on charges of driving under the influence of drugs and alcohol, but the judge in the case said he would grant no further delays.

Superior Court Commissioner Steven Lubell set a new trial date of July 11 for Richie, who was arrested in December after allegedly driving the wrong way on a busy Los Angeles freeway.

Lubell, who pushed back the trial date from June 25 at the request of Richie's lawyers, said he would not put it off again.

Richie, the 25-year-old daughter of singer Lionel Richie who co-stars with best friend Paris Hilton in The Simple Life, was not in court for the brief hearing in Los Angeles.

"She has two options: Either she goes to trial or she changes her 'not guilty' plea," said Jane Robison, a spokeswoman for the Los Angeles County District Attorney's office.

If convicted, Richie faces a minimum punishment of 90 days in jail because she has a prior conviction for driving under the influence, Robison said.

Police say that when they questioned Richie at the time of her arrest she failed a sobriety test and admitted that she had smoked marijuana and taken the painkiller Vicodin.

Although her black sports utility vehicle was pointed in the right direction when officers found her, it matched the description of a car that had been seen entering the freeway against traffic.

Hilton, 26, was sentenced to 45 days in jail for violating her probation in a drunken driving case. She is expected to serve 23 days with standard credit for good behavior behind bars. She sparked a worldwide press frenzy when she was briefly released for what authorities said were medical reasons.

Robison said sensational news coverage around Hilton's jail term was not a factor in Richie's case.

"For us it's taken on a case-by-case basis," she said. "That's a different office, different jurisdiction. It has nothing to do with this case."