Plot hole: Spence comes in with a pizza and says, "Let's hit this pizza hard and get out of here." But then later we find out there's a laptop in the pizza box. What if the guys actually wanted a slice? Also, after the guys leave for the movies, Carrie or Arthur would've seen the laptop in the pizza box. (00:05:35 - 00:06:55)
Continuity mistake: Deacon says "How do we know cutie-pie isn't cutie-guy?" then crosses his arms. In the next shot his arms are immediately uncrossed and on his hips when Doug replies. (00:06:00)
Revealing mistake: In the kitchen, Deacon asks Doug, "Are we gunna play basketball or what?" while leaning against the counter. In this shot you can see the kitchen wall is on an angle slanting away from the camera. This makes the kitchen look bigger and cuts down on the empty stage space on the wall where the cameras are. (00:07:00)
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.