Stewart, 42, told David Letterman last week that the baby girl is due in February.
Stewart and Tracey, a 37-year-old veterinary technician, had their first child, Nathan Thomas, in July 2004.
As for having a daughter, Stewart expressed some reservations on his parenting skills to Letterman. "I don't know that much about women," he said. "A boy child, I feel like I'll know how to deal with it if he has a problem. I'll just be able to say to him, 'Well, repress it,' and he will hopefully swallow that, as I have. And then you figure you have 30 years before it comes out over dinner where somebody spills the gravy and then you're like 'I hate you!'
Whether or not Stewart wants to join in, the little girl will have plenty of room for tea parties: Earlier this year, the Comedy Central star paid $5.8 million for a 6,000 sq. ft loft in Manhattan's Tribeca neighborhood for his family and their two pets.