I've heard they are fine at first when the baby can't really move all that much but then can get dangerous if not tied tight enough/hooked up properly as the baby starts moving around. If you're concerned when the baby is a little bigger I think the breathable bumpers are safer than no bumper at all (arms and legs getting stuck in slats in crib sounds like the worst case scenario to me)!
I plan to have mine in until baby is rolling around and then I'm going to reevaluate. I've heard of babies getting arms and legs stuck between the slats, so I'm afraid to not have anything. Breathable might be the way to go.
You are such a cute preggo! I don't really have an opinion on bumpers - we have one in our crib now, but it's really just for show so I may take it out once the baby starts sleeping in it whenever that is! Just wanted to pop by and say your blog is super cute and thanks for following!