In this article, we will examine a practice that has been neglected in the literature: The announcement of sex in prenatal ultrasounds. Drawing on research in linguistic anthropology, we will propose a vision of the statements announcing the sex through the prism of their performativity, without neglecting the question of the truth of their contents. We will consider the announcement of sex as a practice presenting specific sequential formats in which the announcement itself is systematically followed or preceded by a sequence identifying the modes of visual identification of sex. As a result, we will understand these sequences as allowing us to address the question of the truth of sex through the prism of its visibility and recognizability to parents and as one of the constitutive features of the medical practice.