Evaluation of the cavum septum pellucidum is required in standard second-trimester screening fetal anatomy ultrasound scans. The absence of septum pellucidum triggers further evaluation and referral for subspecialty counseling. Absence of septum pellucidum is linked to other midline anomalies including septo-optic dysplasia. The purpose of this narrative review on absent septum pellucidum and septo-optic dysplasia is to discuss the literature, including pre- and postnatal management and neurodevelopmental outcome, provide practical recommendations, and outline research gaps to advance this nascent field.