First trimester obstetric ultrasonography of a 32-year old female patient revealed a 13-week-old (according to the length of the femur and abdominal circumference) intrauterine live pregnancy with the absence of the fetal head. Medical abortus was performed with the diagnosis of acephaly and final diagnosis was confirmed by pathological and radiological examinations. We present and discuss the possible etiopathologic mechanisms of an acephaly case, which is described as acardia-acephaly complex in the literature, and usually appears in cases of twin reversed arterial perfusion sequence, but has not been previously reported as an isolated finding.