Speaking as a maternity nurse, I dislike seeing siblings hanging around during a delivery. As others have said, labor can take a long time. Even a scheduled c section can be delayed. Unfortunately, we've had some delayed for hours if emergencies happen or the labor wing gets unexpectedly very busy. Scheduled c sections are bumped if a Mom in labor needs an emergency section. So even that can get boring for sibs.
Also, it is rare but sometimes even routine, scheduled sections can have complications. For Mom or baby. So you have to be prepared for that.
Is your friend's DH planning to have another adult there with them? Our hospital does allow siblings in a birth room delivery, but very few families do it. The siblings must go to a class ahead of time & there need to be a seperate adult present, just for the kids. So Dad is there to support Mom, and Grandmom is there for the siblings.
But for a c section, only the Dad would go in. So who would be watching the other kids? They of course can't be left alone in a waiting room (depending on age, of course). And the staff can't be depended to keep an eye on them.
And will Mom be worrying about the other kids & how they are doing the whole time? She certainly doesn't need that extra stress.
Good luck to your friend, Hope everything goes well for her & baby!
