Crib bumpers

So I took a pregnancy class that included SIDS as one of the topics. The speaker told us that nothing should be in the crib except a mattress & fitted sheets. Instead of blankets the baby should be dressed warmly, swaddled, &, if needed, a sheet tucked tightly around the baby & mattress. She also said that any blankets and bumpers on or in the crib could cause the baby to suffocate. However, a lot of pics I've seen ppl post on here of nurseries show bumpers & blankets in the crib. Does anyone know anymore about this topic?