Abstract Objectives: to understand the cultural context presented in hospitals and its relation to the obstetric nurse's autonomous practice on low-risk childbirth care. Methods: ethnographic research performed in three public maternities in Rio Grande do Norte, Brazil. Three managers and twenty-three obstetric nurses participated in this research. Results: distinctive on cultural, organizational and structural aspects of the hospital institution interfering directly with the obstetric nurse's autonomous practice. Among these aspects, professional appreciation on low-risk childbirth care contributes for the nurse's autonomy Conclusions: it was noticed that obstetric nurses undergo different contexts of action, which directly interfere with their autonomy on low-risk childbirth care and their decisionmaking abilities. It is necessary, then, to eradicate the relation of dominance and submission that it is still imposed by medical hegemony.