I imagine you know this, but others might not: Rebecca Riggs (Grayza) actually was pregnant during filming - that's not a prosthetic stomach. So it might very well be that the writers themselves hadn't figured out what her baby "meant", if anything, since they probably wrote the scripts well before they knew that she was pregnant at all. It was probably something of a shock to find out how frelling big she'd be by the start of the shoot!