Objective: Our goal was to present a case series of pregnancy-associated malignant brain tumors. Study Design: A review was conducted from 1978-1998 at 5 hospitals. Results: Ten women were diagnosed with a malignant brain tumor during pregnancy (n = 8) or post partum (n = 2). Patients diagnosed antenatally exhibited severe symptoms, manifest between 27 and 32 weeks’ gestation. Six were emergently delivered of their infants because of maternal deterioration, and 2 were delivered electively in the early third trimester after documentation of fetal pulmonary maturity. There were 4 maternal deaths and 1 neonatal death; all of the other infants maintained viability. Conclusions: Malignant brain tumors rarely occur in pregnancy. In contrast to reports that describe an indolent course, each of the 8 antenatal patients experienced a neurologic crisis. If symptoms are amenable to pharmacologic control, we advocate delivery in the early third trimester after documentation of fetal pulmonary maturity. To minimize temporal lobe or cerebellar herniation in neurologically unstable patients, a consideration should be made for cesarean delivery with the patient under general anesthesia, followed by immediate neurosurgical decompression. (Am J Obstet Gynecol 2000;182:1215-21.)