Com medo de que is often described as a conjunction. This author would say, that this construction is as little a conjunction as "being afraid that", "of fear that" etc.. If all construction of this type were conjunctions, we would have an unlimited number of conjunctions. This author would say that we can only call conjunctions single words or group of words whose components are only used in a restricted context. We include this construction in our list, because it is mentioned very often.