Headache experienced during pregnancy or in women who have recently given birth is usually not cause for concern. But a new study suggests that in this group of women, healthcare professionals should be alert to the rarer and more severe causes of headaches, which may point to a significant underlying health condition.

Eighty-five different types of headache exist, experts say, and about 90 percent of headaches that occur during pregnancy are migraine or tension-type headaches. However, the remaining 10 percent may indicate serious disorders, warranting a complete medical history, examination and referrals to those who can provide neurological expertise. According to one report, neurological disorders were the third most common cause of maternal death, ranked ahead of sepsis, in the United Kingdom between 2006 and 2008.

Migraines typically decrease during pregnancy, but women with migraine are twice as likely to develop preeclampsia — a serious, potentially fatal, pregnancy-related disorder — than those who do not have migraine. The authors stress that during pregnancy, migraineurs should seek medical evaluation if they experience a headache that differs from their typical migraines.

Additionally, the authors caution that headache during pregnancy may be a sign of idiopathic intracranial hypertension, a rare condition in which pressure builds up inside the skull. It can present for the first time during pregnancy and can be fatal if not treated promptly.

Finally, the authors say, pregnancy is a risk factor for cerebral venous thrombosis (CVT), a blood clot in the sinuses that drain blood from the brain.  Headache is the most common symptom in CVT and often the first symptom patients report.

Kirsty Revell, MD, of the Princess Anne Hospital in Southampton, England, co-authored this study, which appeared in May in the journal The Obstetrician and Gynaecologist.