A doctor based at Southampton's university hospitals has warned headaches during pregnancy could "mask" serious underlying health conditions.
Kirsty Revell, a specialist registrar in obstetrics and gynaecology at the Princess Anne Hospital, said 90% of headaches experienced by mums-to-be were a result of migraine or tension and usually improved or stopped during the last six months of pregnancy.
But a small percentage were caused by potentially life-threatening neurological conditions - the third most common cause of death among pregnant women.
In a review published in the journal The Obstetrician and Gynaecologist (TOG), Dr Revell looked at common causes of headaches during pregnancy and the postnatal period, the conditions associated with them and how GPs, midwives and obstetricians should manage care.
"Headaches are common in life and some women find they suffer a lot during pregnancy, but most are benign, for example migraine or tension headaches, and will not harm mother or baby but will just be unpleasant," she explained.
"However, some headache types can be more dangerous and an indication that something is seriously wrong and it is vital GPs, obstetricians and midwives are aware of the signs and symptoms associated with these conditions and know when to seek advice from a specialist."
Dr Revell, who co-authored the review with Dr Paul Morrish, a consultant neurologist in Gloucestershire, said the common occurrence of headaches during pregnancy could mask conditions such as cerebral venous thrombosis - a blood clot in the sinuses of the brain - or pressure build-up in the skull, known as idiopathic intracranial hypertension, which is more likely to occur in obese women of childbearing age.
She also warned that women who experience migraines have a two-fold increased risk of developing pre-eclampsia, a common condition which causes high blood pressure and loss of protein in the urine and can lead to birth complications.
"While it is important not to cause unnecessary alarm or panic, women should be aware that if they suffer from continuous headaches during pregnancy or migraines that are very different their normal type, they should discuss it with their GP or midwife," she said.
"It is at that point we need to be confident health professionals consider all possible causes - including the rarer conditions we've highlighted - to ensure all women receive the correct advice, guidance and treatment."