Married since 2006, Spelling and McDermott, 44, have two children together: son Liam, 4, and daughter Stella, 2.
The 90210 vet concealed her growing baby bump in NYC on Monday, where she and McDermott were promoting their new Oxygen reality series sTORIbook Weddings. The famous couple were coy with UsMagazine.com about expanding their brood.
"They ask us every day!" Spelling added. "It's so funny!
Best part about parenthood? "Every second!" Spelling cooed.
"It's ever-changing," her hubby added.
"It's challenging, but every second is amazing," Spelling told Us in August 2010: "I'm passionate about everything in my life. Obviously my family and my kids are my priority. I want to be that stay-at-home mom, but I want to build an empire at the same time."