O bebê quer trocar

Today while I was sitting in a bakery enjoying a sandwich and a drink, somebody asked why the baby was crying, to which the mother replied, "O bebê quer trocar." (The baby wants changing.). This sentence at first surprised me, because the mother used the verb trocar intransitively in a sense that does not belong to it, at least not according to what my ear and my dictionary tell me. Trocar (to change) can be used transitively (you change something), with the preposition de or pronominally meaning to get changed/to change (clothes). She ascribed to that infinitive a passive meaning is found in a few languages whose infinitives can be easily converted to the passive, as is the case in Latin and the Scandinavian languages. Latin amare means to love, but amari means to be loved. Swedish älska and Danish elske mean to love, but Swedish älskas and Danish elskes mean to be loved. These three languages do not use an auxiliary and a past participle as most languages do (and as English does) to make the passive voice, they simply change the infinitive. A similar phenomenon can be seen in English in the translation of the title of this post: The baby wants changing (or in some dialects: changed). Here I used the gerund form, also known as the -ing form, to mean The baby wants to be/get changed. If I were to give the sentence an active meaning, I would have said The baby wants to change, which doesn't make sense in English, by the way, but that's what that mother said in Portuguese. Another language that has a verb in the past participle, just like English wants changed, is Romanian, where it is possible to say Bebeul trebuie schimbat (The baby needs changed) as well as Bebeul trebuie să fie schimbat (The baby needs to be changed).