Pregnancy is a period of psychological change which may lead to difficulties of adaptation and psychological suffering and give rise to high-risk behaviours for the fœtus in pregnant women. These risk behaviours, which are defined by certain authors as a form of “maltreatment” of the fœtus, usually spring from the psychological distress of the pregnant woman but are not recognised as a specific medical disorder. We illustrate the difficulties encountered in the identification of, and the specific intervention in, these situations through the clinical case of a pregnant drugs-dependent patient subjected to several stress factors who, in addition to consuming substances, developed high-risk behaviours for herself and her pregnancy: self-endangerment under the influence of substances, falls or refusals of treatment. In our first part, we discuss the medicolegal possibilities afforded by French law to protect the fœtus in the event of the future mother's high-risk behaviours. In our second part, we discuss the successive evolutions of the legal status of the fœtus and pregnancy, and their consequences for medical practice and the clinical situations concerned. The lack of an answer concerning the designation of these behaviours, as either medical, legal or social acts, will prompt perinatal practitioners to a certain medicolegal prudence.