Fetal Treatment of Galenic Malformations

The study involves a single fetal intervention of maternal transuterine, fetal transcranial torcular puncture and median prosencephalic vein embolization. Detachable platinum coils (Target XL and XXL Detachable Coil, Stryker Neurovascular) will be used to pack the prosencephalic varix. This procedure will take place in an obstetric OR at Brigham and Women's Hospital. Data will be collected every 4 weeks post-procedure until delivery, as per standard of care. Data regarding delivery and post-delivery status will also be collected until the subject is discharged from the hospital. After delivery, neurological assessments will be performed every 6 months for 2 years (adjusted for gestational age). Data will be compared to historical cohorts.