Originally posted by Panzy:

At first we had the same issue, they just seem to go through the walls sometimes. Especially when giving birth. The mother would poop one out and it just be on the other side. first thing we did was remove any fire near them, if they are spooked they will just ram into the walls and sometimes glitch through. I also built a big pastor and opened the side of the barn so they can graze. we also built a ditch around the base so monsters can't get up aganst the wall. Again to prevent them from freaking out.

Sum it all up.

-remove any fire sources
-prevent enemies from getting close as best as possible
-lots of space so they don't stack or birth through the wall

On a funnier note, we have only one entrance in and out of the pastor and my god, when we run in there. Those piggies just dart for that door !!