Trivia: Kevin James, who plays lead character Doug, and Gary Valentine, who plays his cousin Danny, are in fact real life brothers, with Gary being over 4 yrs older.
Trivia: The house that Doug visits to make a delivery and stays for a while is the same one that is used for the Heffermans' neighbours' house.
Trivia: In many episodes when Doug is hurt, startled, angry etc., he will yell "Yuspa." Cathy Yuspa is one of the two writers on the show.
Trivia: When Spence is describing why he can't eat peanuts ("My body doesn't like this and my throat gets real small") Kirby's hands are mimicking the lines along with Spence because he already knows what Spence is going to say. (00:51:40)
Trivia: Carrie is talking about being able to fit the furniture in the baby's room, after she says she picked up a few boxes from the supermarket, she says Shalmonie Cuitsis sends them congratulations. Shalmonie is a game Doug made up when pretending to read in the episode 8 in Season 1 "Educating Doug".
Trivia: The picture that Doug brings to the high school reunion is a picture of Leah Remini from the magazine Stuff in real life. You can see it when Doug shows the picture to his friend at the reunion. Carrie Heffernan is hot, but was probably not on the cover of Stuff magazine.
Trivia: Doug's parent's house is the same one used as Deacon's house.
Mild Bunch - S9-E9
Trivia: In this episode, Adam Sandler guest stars as one of Doug's old high school friends. In an earlier scene in the video store, the movie "Punch Drunk Love," which stars Adam Sandler, can be seen on one of the shelves.
Answer: To answer the question directly. Carrie and Doug do not have a biological child during the show's main run. In season 3 or 4 finale (cant remember which) Carrie has a miscarriage. Later on in the show they find out Carrie has 1 working ovary. Thus reducing the chance of them conceiving. By the final season, they couple agree to adopt from China and go to collect their child in the show's final episode. While on the flight back from China it's revealed that Carrie is once again pregnant. However the last scene of the show is a flash forward showing that Carrie goes full term with that child and they are struggling with both kids.
Ssiscool ★
Adding on to this answer, I read somewhere that producers were afraid of the show having a "before baby" feeling and then an "after baby" feeling. Some fans feel that main characters, or the show in general, decline in quality after a major change. For example, Jesse and Rebecca on "Full House" after they had twin sons, and Daphne on "Frasier" after she married Niles.