Deeley is pregnant with her husband Patrick Kielty's baby.
"Exciting news....Paddy and I are so happy to be expecting our first child in the Spring....." Deeley, 38, announced on Twitter Thursday. "Lucky us."
Shortly afterwards, Deeley posted a photo on Instagram of a screenshot that showed a text message exchange between herself and a SYTYCD producer. The producer, Jim Breen, clearly poked fun at the dietary restrictions for pregnant women.
"Jeff and I are going to a soft cheese and shellfish party. Want to come?" he said.
Deeley captioned the photo, "My producer's response to our exciting news! I laughed till I cried! You don't want to know my reply!"
The British television personality wed Kielty, a 44-year-old Irish comedian, in a hush-hush ceremony in Rome, Italy, in October 2012.
The couple first met in 2002 when they hosted the U.K.'s Fame Academy reality series together. Deeley and Kielty reportedly began dating in 2011.
So You Think You Can Dance's final twelfth-season performance show airs Monday, September 7 at 8PM ET/PT. The show's finale broadcast airs the following week, September 14, when one winner will be crowned "America's Favorite Dancer."