Occipital mass in antenatal sonography

Biophysical profile (BPP) with ultrasound performed for a 32-year-old G5P3013 admitted at 31 weeks gestation with preterm, premature rupture of membranes (PPROM) noted an extracalvarial mass concerning for an encephalocele. Fetal MRI demonstrated edema over the occiput with no definable lesion visualized. Preterm labor requiring Cesarean delivery resulted in a live male neonate at 33 weeks gestation. An occipital mass was observed on neonatal physical exam. Postnatal ultrasound and MRI were consistent with cephalohematoma. This was surprising given the lack of vaginal delivery. We hypothesize that the occiput was positioned against the maternal ischial tuberosity and developed chronic trauma secondary to normal fetal movement over time, resulting in a cephalohematoma. Postnatal imaging confirmed this diagnosis as the mass gradually decreased and ultimately resolved. Although other etiologies are possible, this case emphasizes the need to consider cephalohematoma in the differential of CNS masses during pregnancy without abdominal trauma and/or vaginal delivery.