The case of a 25-year-old primipara in the second trimester of pregnancy, suffering from a peripheral primitive neuroectodermal tumour (pPNET) diagnosed by bone biopsy, is described. External irradiation was initially performed because of Jacksonian seizures due to a lesion in the right cerebral hemisphere. Appropriate shielding was used to reduce fetal exposure during brain radiotherapy. Caesarian delivery at the 27th week of gestation was performed because of tumour progression. The neonate had no evidence of disease and survived for 1 month. However, the placenta and ovaries showed metastases from the maternal pPNET. The patient died 14 months after initial diagnosis owing to the aggressiveness of the tumour, the rapid and extensive semination (bone marrow, lung, liver, craniospinal axis involvement) and the inability to adequately treat the patient with appropriate doses of chemotherapy.