Although the incidence of cerebral and spinal tumours is probably no greater than at other times, some tumours expand during pregnancy and may present unusually rapidly. This probably reflects a mixture of hormonal and vascular factors; most meningiomas and some neurofibromas and gliomas express oestrogen and progesterone receptors and placental growth factor.

Neurofibromatosis type 1 presents particular problems in pregnancy. Women with this condition experience an increased rate of spontaneous first trimester abortions, perhaps also intrauterine fetal growth retardation and stillbirths, and have a high rate of caesarean section. Most women notice that cutaneous neurofibromas grow or appear de novo during pregnancy.

Meningiomas are particularly liable to expand in the third trimester, causing local mass effects such as headache, cranial nerve palsies, hemiparesis, or paraparesis, which may remit after delivery. Corticosteroids can be given to reduce surrounding oedema, and surgery can often be delayed until after delivery. Gliomas tend to present earlier in pregnancy and have a reputation for following an aggressive course. They may require early surgical intervention, and it is sometimes also appropriate to consider termination of the pregnancy. Women with known intracranial mass lesions require careful assessment prior to delivery: prolonged Valsalva manoeuvres can increase intracranial pressure and elective caesarean section may be necessary.

Choriocarcinoma is a tumour peculiar to pregnancy and the most common form of malignancy associated with pregnancy. It usually presents after molar pregnancy or abortion, but 15 per cent of cases occur during or after normal pregnancy. Neurological manifestations due to brain or spine metastases are common. The brain metastases have a tendency to invade blood vessels, giving rise to strokes through infarction or haemorrhage. Spinal metastases cause cord or cauda equina compression that may be rapid in onset. There are usually multiple pulmonary metastases on chest radiography and the serum chorionic gonadotrophin is greatly elevated. Early diagnosis and treatment (with chemotherapy and radiotherapy) improves survival, but the mortality rate of cases with neurological manifestations remains high.

The normal pituitary gland and some pituitary tumours such as prolactinomas expand during pregnancy.