Catherine, Duchess of Cambridge makes an official visit to The Guildhall with Prince William, Duke of Cambridge on November 28, 2012 in Cambridge, Cambridgeshire. Credit: Mark Cuthbert/UK Press via Getty Images

Put another candle on the cake for Kate Middleton!

The pregnant Duchess will have a lot to celebrate when she turns 31 on Wednesday, Jan. 9, her first birthday as a mom-to-be. But don't expect a big royal bash in her honor.

Prince William's wife will be "spending her birthday privately," a St. James's Palace rep tells Us Weekly.

In fact, the celebration is likely to be even more subdued than last year's intimate dinner for family and friends at Kensington Palace. "She just wants something low-key," a source tells Us. "I suspect she will spend it at her parents' house." (Carole and Michael Middleton live in Bucklebury, Berkshire.)

Of course, the Duchess of Cambridge already got the greatest gift of all: the news that she and Prince William, 30, will be parents in 2013.

"Trying for a baby has been their priority," a royal confidant told Us of the couple in December. "They're both excited to be focusing on a new chapter in their lives."