Acalvaria Is a rare congenital disease considered as a post-neurulation defect: It consists of the absence of Calvary bones, dura mater and associated muscles in the presence of a normal skull base and facial bones normal. Currently, there is no identified cause of Acalvaria. The main putative pathogenesis is the problematic migration of the membranous neurocranium from the normal positioning of the immature ectoderm. Although the malformation has been fatal to date with only a few survivors, the prenatal diagnosis of Acalvaria is of rather remarkable importance as it allows clinicians to plan appropriate and timely management. So that this fetus can benefit from surgical advances.