(Cover) - EN Showbiz - Nicole Richie has thrown a party to celebrate her son’s first birthday.

The TV star-turned-fashion-designer chose to mark Sparrow’s big day on Saturday, even though his birthday isn’t until September 9. Nicole and her fiancé Joel Madden held the bash at their home in the Hollywood Hills, and their garden was decorated with green, orange, red and purple balloons festooned with Happy Birthday.

The couple – who also have a two-year-old daughter, Harlow - organised a low-key party for their young son and were careful not to go overboard with the celebrations.

"Nicole was keeping the party simple to not overwhelm Sparrow," a source told People magazine. "Everyone seemed to have a great time."

Around 50 guests were invited to the event, including Joel’s brother Benji Madden and actress Ellen Pompeo, along with her 11-month-old daughter Stella Luna.

The party were treated to a host of tasty snacks along with a special birthday cake for Sparrow. (C) Cover Media