Mid-trimester fetal subdural hemorrhage: prenatal diagnosis.

A routine antenatal ultrasound examination at 20 weeks' gestation revealed a space-occupying lesion in the fetal right cerebral hemisphere. The borders of the mass were indistinct and there was no midline shift. A small collection of echogenic bowel was identified at the right iliac fossa. In an attempt to explain both findings a provisional diagnosis of a fetal blood dyscrasia was made. Fetal cranial magnetic resonance imaging 24 h later confirmed the diagnosis of a subdural hemorrhage. Subsequent fetal blood sampling confirmed severe fetal thrombocytopenia. To our knowledge this is the first report of the antenatal diagnosis of spontaneous mid-trimester fetal subdural hemorrhage.