Queasy Rider - S2-E1
Visible crew/equipment: When Doug is looking at the bike for the first time, all the stage lights are reflected in the helmets on the table. (00:06:00)
Queasy Rider - S2-E1
Visible crew/equipment: When Carrie gives Arthur the iron, six stage lights are reflected in the iron itself. (00:06:25)
Queasy Rider - S2-E1
Visible crew/equipment: When Doug comes into the garage and falls over for the first time, a tape marker is visible on the floor. (00:07:05)
Queasy Rider - S2-E1
Visible crew/equipment: When Doug and Carrie are arguing over the bike a white tape marker can be seen on the floor. (00:09:20)
Queasy Rider - S2-E1
Visible crew/equipment: When Doug is telling Carrie that he hates the bike, a crew member in blue jeans can be seen in the back of the mirror on the bike. (00:18:55)
Queasy Rider - S2-E1
Visible crew/equipment: During this entire episode, you can see lots of stage lights reflected in the motorcycles chrome parts.
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.