Why does pre-eclampsia cause severe headache in pregnancy?

Pre-eclampsia affects the blood vessels and can raise blood pressure. These changes may disturb the way the brain regulates blood flow, producing a severe, persistent or throbbing headache. The pain may not improve with rest or usual simple measures. It can occur with blurred vision, flashing lights, upper-abdominal pain, nausea, swelling or breathlessness.

Headache in pregnancy can also result from dehydration, poor sleep, migraine, infection or other causes. The symptom cannot identify its cause without assessment. A clinician may check your blood pressure, urine, reflexes and blood tests, then decide whether further monitoring is needed.

Tell your maternity team promptly about a severe, new or persistent headache, especially if it feels different from headaches you have had before. Note when it began, how long it lasts, whether light affects it, and any vision or abdominal symptoms. Use only medicines approved for you in pregnancy and follow the dose advice from your clinician.

Resting in a quiet room and drinking fluids may help some ordinary headaches, but should not delay assessment of a severe or unusual headache. Do not rely on symptom relief alone to judge whether pre-eclampsia is present.

Seek urgent maternity assessment for a severe headache that persists, suddenly becomes intense, or occurs with vision changes, confusion, weakness, seizure, fainting, breathlessness, severe upper-abdominal pain or reduced fetal movement. Ask someone to accompany you if you feel unwell, and avoid driving if your vision or alertness is affected.

Ask: What is my blood pressure and does it need repeating? Could this headache have another cause? Which pain-relief options are suitable? What changes should prompt immediate return to maternity care?