This article discusses how cervical scarring can cause failure to progress. This actually happened to my sister. I had never heard of it before that. If your provider knows to look for it, it can be resolved in many cases. In my sister's case it was discovered 14 hours in to labor. Many hours and painful exams to break up the tissue later, she gave birth vaginally. I thought I would pass along the information in case it might help someone else.