Strike Out - S3-E7
Continuity mistake: The bottle of Lipton Ice Tea on the table rotates on its own without anyone touching it. (00:03:20)
Strike Out - S3-E7
Continuity mistake: When Arthur sits down for his meal, there is a bottle on the table. The lid is either on or off depending on the shot. (00:03:30)
Strike Out - S3-E7
Continuity mistake: After Doug says "Let's hit the streets", Doug, Arthur, Deacon and Kirby go on a mini crime-spree. During this montage each characters outfit completely changes several times. They are also dressed very lightly for late October/early November in New York. (00:13:00 - 00:14:00)
Visible crew/equipment: During the flashback, while Doug is waiting on the porch Carrie rushes out then gets into her car to take off, and in the next shot facing the front door, the reflections of the camera operator, wearing a white baseball cap, and the camera are visible on the window. (00:12:35)
Visible crew/equipment: During the flashback, when Carrie walks over to Doug at the side of the house, and he zips himself up, in shots facing Doug, a crew member and production equipment are visible on the right side of the screen. (00:20:10)
Visible crew/equipment: When Doug sneaks out of Carrie's house and finds her having a cigarette by the car, a boom mic shadow can be seen on the bush beside Doug. (02:53:45)
Continuity mistake: When Carrie suggests about them looking after the kids to Doug, he has his arm up by his chest. When the camera changes it's lowered. (00:04:20)
Visible crew/equipment: When Carrie notices that Doug has walked out the room, there are some tape markers on the floor from where Doug was stood. (00:09:40)
Continuity mistake: When Carrie is serving up the burgers for dinner, she places one on Kirby's plate. Camera cuts to Kirby sitting down and the burger has vanished. (00:10:25)
Continuity mistake: Carrie cuts Kirby's burger in half with a knife in her right hand. Camera cuts and a fork has appeared in her left hand. (00:10:30)
Continuity mistake: When Carrie say to Doug that they are sleeping on the fold out couch, her arm goes from on her hip to hanging by her side instantly. (00:11:00)
Continuity mistake: When Doug and Carrie are in Deacon's kids' room, Carrie is changing the baby and between shots the baby changes from lying down to sitting up. (00:15:00)
Continuity mistake: When Doug and Deacon both volunteer for the calendar the magazine on the bench is constantly changing position without being touched. (00:05:10)
Continuity mistake: Carrie asks Doug what he's doing when she walks into the bedroom. She then hangs her coat on a hanger and has the coat in her hands (as seen in her reflection in the mirror). Camera changes and she's shutting the wardrobe. (00:08:01)
Audio problem: When Doug is having his photo taken the guy taking the photos doesn't actually press the button on the camera but the sounds are heard. (00:15:40)
Continuity mistake: When we first see Lou, he is pushing some rubbish down into the bin, camera cuts and he now has a box in his hand. (00:00:05)
Continuity mistake: The Heffernans have a double garage as witnessed in any scene in the garage. However, in this episode at the start they only have a single garage. (00:00:30)
Continuity mistake: The Heffernans have neighbors on both sides of the house as seen in previous episodes. However there is no house to the left of theirs when we see Lou at the very start. (00:00:40)
Continuity mistake: When Doug goes to get Carrie's present from the closet her position on the bed changes between shots. (00:05:30)
Continuity mistake: When Carrie gets her camera it changes position in her hands before she turns it around. Note the strap, it goes from left to right. (00:06:00)
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.