Headaches are a very common presenting complaint in pregnancy, with over a third of women affected.
Similar to the non-pregnant population primary headaches account for most cases, however at least a third of gravid headaches are secondary to other pathologies.
Fortunately, the majority of these have benign causes like viral infection and sinusitis but due to the significant morbidity and mortality associated with certain conditions in pregnancy all cases should be taken seriously, and recognition of red flags is key.
Primary headaches in pregnancy
Most headaches in pregnant women have no sinister underlying pathology, and migraine and tension-type headache are the most prevalent diagnoses in early pregnancy (it is worth nothing that migraines pre-pregnancy are a risk factor for hypertension and pre-eclampsia).
Primary headaches peak in women of reproductive age anyway due to the impact of hormones, however 75% of women who experience benign headaches pre-pregnancy find they reduce in the antenatal period.
However, it is important to note that previously diagnosed primary headache disorders can present with different symptoms in pregnancy so all need to be fully assessed.
Secondary headaches in pregnancy
Hypertensive
Pre-eclampsia and eclampsia
The presentation is variable but most commonly a worsening bilateral pulsatile headache, which can affect one or more scalp areas. Pain can be worse with exercise and doesn’t improve with mild analgesics.
Visual disturbance may be present, along with other signs of end organ damage or seizures. Due to the heterogenous presentation any woman over 20 weeks gestation presenting with a headache should have a blood pressure measurement and urine dip to rule out pre-eclampsia.
Posterior reversible encephalopathy syndrome
A clinical phenomenon comprising a progressive headache, reduced consciousness, visual disturbance, seizures, vomiting and focal neurology. Women usually have a concomitant gravid hypertensive disorder or renal failure, and the syndrome is accompanied by a characteristic MRI appearance which can persist beyond the resolution of symptoms.
Vascular
Ischaemic stroke
Around a third of strokes have transient headache as a presenting feature, but neurological signs are much more common and allow easier recognition.
Diagnosis and treatment are similar to non-pregnant stroke patients although pregnancy is a relative contraindication to thrombolysis so a senior MDT decision is required.
Subarachnoid haemorrhage
As in non-pregnant patients SAH is characterised by a thunderclap headache, vomiting and loss of consciousness. Risk of SAH is around 20 times higher in the postnatal period compared to the general population.
Cerebral venous sinus thrombosis
There is no specific pattern of symptoms for CVT, which is caused by blockage of blood draining from the cerebral sinuses, mostly commonly patients present with diffuse worsening headaches but not exclusively. Usually patients also have focal neurology, signs of raised intracranial pressure or subacute encephalopathy.
The other risk factors for VTE still apply in the pregnant population and are assessed at set times throughout pregnancy so should be taken into account when considering CVT. Patients with suspected CVT should urgent CT or MR angiography and treated with anticoagulants.
Reversible cerebral vasoconstriction syndrome
Commonly a recurrent, sudden, severe headache starting in the first week postnatally and triggered by exercise, sexual intercourse, straining or strong emotion.
Cervical artery dissection
A rare diagnosis which most commonly occurs due to pressure in labour and is accompanied by a sudden severe unilateral headache.
Space-occupying lesions
Brain neoplasms must be at least 1cm in size to cause mass effect symptoms, and certain types can enlarge in pregnancy, meaning this may be when a woman presents with signs of intracranial hypertension. The most common primary brain tumours diagnosed in pregnant women are pituitary adenomas, meningiomas and glial tumours.
Although much rarer, pregnancy-associated tumours like choriocarcinoma can also metastasise to the brain, causing pain, dizziness and visual loss.
Red Flags
Researchers have studied primary and secondary headaches to try and find strong differentiating factors, however this has proven difficult. It is thought that unilateral headaches are more likely to be benign but features which are common in primary headaches, such as visual and sensory disturbance, can also occur with more sinister causes.
Therefore, a thorough history and examination, including a full neurological examination, along with basic investigations (blood pressure, urinalysis, bloods, fundoscopy) are key to identifying women who need further investigations.
Specific to pregnant patients:
- Rapid onset (reaches peak within 5 minutes) or very severe
- No headache history pre-pregnancy or new type of headache
- Varies with posture
- Wakes the patient from sleep
- Triggered by exertion
- Third trimester
- Hypertension
- Proteinuria
- Deranged blood results – LFTs, platelets
Common to the pregnant and non-pregnant populations:
- Fever
- New neurological symptoms
- Signs of raised intracranial pressure – nausea, papilloedema
- Comorbidities – cancer, HIV, pituitary disorders, VTE risk factors
Investigations to consider when suspecting significant pathology
- CT or MRI head – CT head commonly first line as more readily available and the fetal risk from a maternal CT head is actually quite low.
- Iodinated contrast can affect the foetal thyroid so should be avoided if possible – if it cannot be avoided a heel prick test of the baby’s thyroid function should be done after delivery.
- CT or MR angiography
- Carotid artery ultrasound
- Lumbar puncture
- EEG
- D-dimers are usually avoided in pregnancy as they can be raised due to changes in the coagulation pathways – occasionally can be useful to rule out thrombotic conditions in patients presenting with an isolated headache but not a common investigation
General management of headache in pregnancy
- Management heavily depends on the suspected underlying cause
- Conservative – minimise triggers, physical activity, regular sleeping patterns, healthy diet, acupuncture, yoga
- Analgesia – paracetamol is the safest option in pregnancy, with codeine and tramadol as second-line options.
- NSAIDs are generally avoided in pregnancy due to the risk of early miscarriage and premature closure of the ductus arteriosus, however there are some circumstances in which they are used before 32 weeks but this decision should only come from a senior clinician after discussion with the patient.
- Prophylaxis – propranolol is first-line for migraine prevention with amitriptyline as an alternative
Key points
- Headaches are very common in pregnancy and most are benign but the significant consequences of certain conditions mean all patients should have thorough history and examination
- Migraine, with or without aura, and tension-type headaches are the commonest forms of primary headache
- Viral infections are the most frequent secondary headache but other important diagnoses to consider include hypertensive disorders of pregnancy, stroke, cerebral venous thrombosis, intracranial haemorrhage and space-occupying lesion
- Early imaging if a sinister cause is suspected is vital for treatment to be most effective
References
(1) Raffaelli, B., Siebert, E., Körner, J. et al. Characteristics and diagnoses of acute headache in pregnant women – a retrospective cross-sectional study. J Headache Pain 18, 114 (2017).
(2) Sandoe, C.H., Lay, C. Secondary Headaches During Pregnancy: When to Worry. Curr Neurol Neurosci Rep 19, 27 (2019).
(3) Negro A, Delaruelle Z, Ivanova TA, et al. Headache and pregnancy: a systematic review. J Headache Pain. 2017;18(1):106.
(4) Hamilton K. Secondary Headaches During Pregnancy and the Postpartum Period. Practical Neurology. May 2020
(5) Wiles R, Hankinson B, Benbow E, Sharp A. Making decisions about radiological imaging in pregnancy BMJ 2022; 377 :e070486 doi:10.1136/bmj-2022-070486