what were they doing to the pregnant women?

There is certainly some value in the fetus or Elaine would have been harvested early but a young undeveloped brain is no use to their machines. So my best guess would be a stem cell theory in that this unborn would have been minced up and used for repairs of their more important control brains.

Machine class brutality.

If you noticed the one creature that ate the red brain did something to it. I believe that was her boyfriend and when he put his hand over her stomach he could feel the heartbeat. So when the others were coming by he/it was protecting her from the others. When I rewatched it again I forgot how it ended and now seeing that ending I can't wait for a sequel but why 4 years? I hope he can keep the others off for abit and maybe they can get away. Plus not sure how long jarrod's brain will keep him like that. If they need brains why not go after some of the animals? They have them unless they need ones that can think.