Nicole Richie was arrested in December

When asked by ABC Television's Diane Sawyer if she was pregnant, the 25-year-old replied: "Yes, I am. We are. I'm almost four months."

Last week, the adopted daughter of singer Lionel Richie was sentenced to four days in jail.

She pleaded guilty to charges of driving while intoxicated.

The star was also handed three years' probation, fined $2,048 (�1,010) and ordered to complete a drug and alcohol programme by February.

She was arrested in December after driving the wrong way down a Los Angeles motorway.

Richie's sentence, which she will complete in September, comes weeks after her Simple Life co-star Paris Hilton was released after spending 23 days in prison for violating probation by driving with a suspended licence.

The ABC interview will be broadcast on Thursday and Friday.