Abstract
OBJECTIVE: Fetal macrocephaly (HC Z-score ≥ +2) is a common reason for referral for neurosonography. While most cases are benign and asymptomatic, syndromic macrocephaly poses a significant risk of abnormal neurodevelopment. This study aimed to describe the sonographic and genetic features of fetuses at the highest risk of syndromic macrocephaly. METHODS: We retrospectively analyzed 19 fetuses with either HC Z-scores ≥ +2.5 or those with ≥ +2 and associated anomalies, evaluated between January 2015 and October 2024. Assessments included fetal neurosonography, anomaly scans, MRI, and genetic work-up. Outcomes and postnatal/postmortem data were reviewed. RESULTS: Mean gestational age at the time of diagnosis was 29.6 weeks (range 23-35.4 weeks). Seventeen fetuses (89%) had associated anomalies: large for gestational age (12/19), callosal abnormalities (11/19), malformation of cortical development (13/19), and facial dysmorphism (11/19) were diagnosed. Genetic investigation results (CMA) were available for 17 of the 19 patients. Overall, 14 of the 17 patients had abnormal genetic findings, mostly involving mTOR pathway genes. CONCLUSION: High Z-scores and additional imaging findings strongly correlate with genetic abnormalities, most often mTOR-related. These results support the integration of exome sequencing into prenatal evaluation of fetal macrocephaly.