Kate Middleton is expected to have a royally relaxing birthday celebration Wednesday.
"She just wants something low-key," a source told Us Weekly about how the mama-to-be will ring in 31.
"I suspect she will spend it at her parents' house."
Next year's birthday plans will definitely be a bit more exciting, as the duchess and hubby Prince William, 30, are expecting their first child later this year.
"Trying for a baby has been their priority," another source told the magazine. "They're both excited to be focusing on a new chapter in their lives."