Diagnostic yield and imaging: aetiology correlations in prenatal intracranial haemorrhage–a retrospective cohort study

OBJECTIVE: To characterise aetiologies and prenatal neuroimaging findings in fetuses with intracranial haemorrhage (ICH), and evaluate the ability of imaging to suggest underlying causes. METHODS: We retrospectively reviewed fetuses with ICH diagnosed prenatally at a single tertiary fetal centre between 2015 and 2025. Cases with a known mechanism at presentation were excluded. Ultrasound (US) and MRI images were reassessed by fetal medicine and neuroradiology specialists blinded to aetiology. Clinical, laboratory, genetic, autopsy and placental findings were integrated to determine underlying causes and assess imaging patterns. RESULTS: Sixty-seven fetuses were included; a definitive aetiology was identified in 38.8% (26/67). Genetic aetiologies were detected in 27.7% (13/47) of cases with advanced genetic testing, most commonly associated with cerebral small vessel disease (CSVD). Other causes included infection (5/67, 7.5%), fetal anaemia (6/67, 9%), and coagulopathy (3/67, 4.5%, of which one was genetic). Twenty-one cases (31.3%) remained unexplained despite comprehensive investigation, and 20 (29.9%) had incomplete investigations. Intraventricular haemorrhage (IVH) was present in 91% (61/67), with periventricular haemorrhagic infarction (PVHI) in 55.2% (37/67). CSVD was associated with multifocal PVHI, porencephaly, white matter injury and frequent brainstem involvement. In fetal anaemia, cerebellar haemorrhage was common, with brainstem and vermian involvement predominantly in non-parvovirus cases. Intraparenchymal haemorrhage without IVH occurred mainly with coagulopathy or infection. Although some phenotypic clustering was observed, there was substantial overlap among aetiologic groups. CONCLUSION: Genetic disorders, particularly CSVD, account for a significant proportion of prenatal ICH, supporting routine genomic testing. Imaging can suggest probable causes, but overlap limits its diagnostic specificity.