As far as Walmart goes, they are very much at fault here. I have gone to a Black Friday at Walmart before. I have known plenty who have & the stories are always the same.
The store is horrible with actually maintaining a line outside. The employees tend to hide in the store & hope the cops will keep it orderly outside.
The next mistake they make is not handing out any vouchers for the doorbuster items. In all honesty it does not pay to stand in line there. If you show up just as they are about to open the doors, you will have just as good a shot as the person who camped out from the night before. This is why you see this store have bumrushes across the country while other stores don't.
The next mistake they make is purposely blocking many of the aisles & departments from being used. Many people are usually flocking to the electronics department. This causes 1000+ people to stay in a very compact space trying to get what they want.
They keep the doorbusters behind the counter so people flock around like a mosh pit. I've seen & heard where they will ask who wants for instance this laptop (enter the big doorbuster laptop model) & people are all going me, me. They will then toss it into the crowd & all hell breaks loose even more.
What is disgusting is seeing parents send their kids to do their dirty work. I saw a few parents scold & insult their child(ren) for not getting what they came for. These people act like animals.
So yes, Walmart is very much responsible for these activities. They see the same results every year yet keep engaging in the same practices. As far as the pregnant woman goes, she should not have to think if I go shopping, I might die or lose my child.
I know if I ever participate in Black Friday in person, Walmart will be the one store I will not bother with.