Picture this: you're a junior doctor in a busy GP practice. A 34-year-old woman, 35 weeks into her first pregnancy, comes in complaining of a headache and nausea. She’s otherwise fit and well. While waiting, she took a paracetamol, and by the time you see her, she says she feels fine.
You take her observations:
Her physical exam is completely normal. It’s tempting to put it down to the stresses of late pregnancy, advise rest, and send her home. But that single blood pressure reading is a major red flag that could signal a life-threatening emergency for both mother and baby.
In the real-life case this is based on, the patient was sent home. The next day, she suffered multiple seizures and was rushed to A&E in a critical condition. This scenario highlights why understanding hypertensive disorders in pregnancy isn't just for exam success—it's essential for safe clinical practice. Let's break down what you need to know.
What is Pre-eclampsia? A High-Yield Definition
When you encounter high blood pressure in pregnancy, you're faced with a key diagnostic challenge. Is it chronic hypertension, simple gestational hypertension, or the one we can't afford to miss: pre-eclampsia?
Pre-eclampsia is a multi-system disorder that occurs after 20 weeks of gestation. It's defined by the new onset of hypertension and the presence of one or more of the following new-onset conditions, which are signs of end-organ dysfunction:
Significant Proteinuria: An albumin:creatinine ratio (ACR) of ≥8 mg/mmol or a protein:creatinine ratio (PCR) of ≥30 mg/mmol.
Renal Impairment: Serum creatinine ≥90 µmol/L.
Liver Dysfunction: Elevated transaminases (ALT or AST) to more than twice the upper limit of normal, often with right upper quadrant or epigastric pain.
Neurological Complications: This includes severe, persistent headaches that don't respond to simple analgesia, visual disturbances (like flashing lights or blurred vision), or clonus.
Haematological Disturbances: Thrombocytopenia (platelets <100 x 10⁹/L) or evidence of haemolysis (like raised LDH).
Fetal Growth Restriction: Due to placental dysfunction.
This condition affects around 2-4% of pregnancies in developed countries and is a leading cause of maternal and fetal morbidity and mortality. While the exact cause is still being researched, most theories point towards abnormal development of the placenta.
Gestational Hypertension vs Pre-eclampsia: Spotting the Difference
It's a common point of confusion, but the distinction is critical.
Gestational Hypertension: This is new-onset high blood pressure (≥140/90 mmHg) appearing after 20 weeks of pregnancy without any of the features of end-organ dysfunction listed above (e.g., no significant proteinuria).
Pre-eclampsia: This is gestational hypertension with evidence of end-organ damage.
Think of gestational hypertension as a warning sign. While it can be benign, a significant number of women with gestational hypertension will go on to develop pre-eclampsia, so they require close monitoring.
The Red Flags: Pre-eclampsia Symptoms and Diagnosis
Actively looking for the signs of pre-eclampsia is key. While some women are asymptomatic, common symptoms you should always ask about include:
Severe headache: Often frontal, throbbing, and unresponsive to paracetamol.
Visual disturbances: Flashing lights (photopsia), blurred vision, or blind spots (scotoma).
Sudden swelling (oedema): Especially of the face, hands, or feet.
Epigastric or right upper quadrant pain: This can indicate liver capsule stretching.
Nausea or vomiting.
If you suspect pre-eclampsia, your initial investigations should include a urine dipstick for protein, followed by a formal ACR or PCR, and blood tests to assess for end-organ damage: Full Blood Count (for platelets), Urea & Electrolytes (for renal function), and Liver Function Tests.
When to Admit? Following NICE Guidelines for Urgent Hospital Referral
The NICE guidelines (NG133) are very clear on this. Your threshold for referring a pregnant woman for urgent hospital assessment should be low.
Refer immediately if:
She has a blood pressure of ≥160/110 mmHg.
She has a BP >140/90 mmHg along with any of the symptoms or signs suggestive of pre-eclampsia (e.g., headache, visual changes, proteinuria on dipstick).
If the BP is in the 140/90–159/109 mmHg range and the patient is completely asymptomatic with no proteinuria, you may consider outpatient investigation. However, this should be done with a clear plan for rapid follow-up and a low threshold for admission if any features of pre-eclampsia develop.
How to Treat Pre-eclampsia: Emergency Management Protocol
Once a patient with severe pre-eclampsia arrives in hospital, the goal is to stabilise the mother to allow for the safe delivery of the baby, which is the only definitive cure. Management involves a coordinated effort on the labour ward or high-dependency unit.
First-Line Antihypertensive Drugs in Pregnancy (UK Practice)
For severe hypertension (BP ≥160/110 mmHg), treatment must be started promptly (within 30-60 minutes) to prevent complications like stroke. The aim is to lower the BP to below 150/100 mmHg. According to NICE, the main options are:
Labetalol (oral or IV): Often the first choice. It's a combined alpha- and beta-blocker. Avoid in women with asthma.
Nifedipine (oral): A calcium channel blocker. A good alternative if labetalol is contraindicated.
Hydralazine (IV): A direct vasodilator, typically used if first-line options are not effective or available.
Preventing Seizures: Magnesium Sulphate for Eclampsia Prophylaxis
If a woman has severe pre-eclampsia, we need to prevent progression to eclampsia (seizures).
Magnesium sulphate (MgSO₄) is the anticonvulsant therapy of choice. It is indicated if there are signs of impending eclampsia, such as severe headache, visual disturbances, or clonus.
The standard UK dosage is:
Loading dose: A 4g IV bolus given over 5-15 minutes.
Maintenance dose: An IV infusion of 1g per hour, typically continued for 24 hours after the last seizure or after delivery.
Remember to monitor for signs of magnesium toxicity (loss of deep tendon reflexes, respiratory depression, oliguria) and have the antidote, calcium gluconate, available.
Eclampsia: The Obstetric Emergency
Eclampsia is the onset of tonic-clonic seizures in a woman with pre-eclampsia. It's a life-threatening emergency. It's crucial to remember that 20-38% of patients with eclampsia do not have classic signs of pre-eclampsia beforehand, so a lack of a prior diagnosis does not rule it out.
Eclampsia Emergency Treatment Protocol
If your patient starts seizing:
Call for help! This is a multi-person job. You need an obstetrician, an anaesthetist, and experienced midwives.
Secure the patient (ABCDE approach): Protect her from injury, secure the airway (e.g., with a head-tilt-chin-lift, consider a Guedel airway), and give high-flow oxygen. Monitor oxygen saturation.
Administer Magnesium Sulphate: This is the first-line treatment to terminate the seizure and prevent recurrence. Give the standard 4g IV bolus. It is far more effective than benzodiazepines or phenytoin.
Control Blood Pressure: Treat severe hypertension as outlined above.
Stabilise and Deliver: Once the mother is stabilised (seizures controlled, BP managed), plans must be made for urgent delivery of the baby and placenta, regardless of gestational age. This is the definitive treatment.
Key Takeaways for Your Next On-Call Shift
Don't ignore hypertension in pregnancy. A reading of 155/110 mmHg is never "a bit high"—it's a medical emergency until proven otherwise.
Actively look for pre-eclampsia. In any pregnant woman with hypertension after 20 weeks, ask about headaches and visual changes and check their urine and bloods.
Know the admission criteria. Any sign of pre-eclampsia or a BP ≥160/110 mmHg means an urgent referral to hospital.
Remember the key drugs. Labetalol for blood pressure, and Magnesium Sulphate for preventing and treating eclamptic seizures.
Mastering the management of pre-eclampsia is a core skill for any junior doctor. Understanding the underlying principles and the clear steps laid out in NICE guidelines will give you the confidence to act decisively when you face this challenging clinical scenario on the wards.
Sources:
Gestational Hypertension and Preeclampsia
ACOG Practice Bulletin
Preeclampsia—Pathophysiology and Clinical Presentations: JACC State-of-the-Art Review
Hypertension in Pregnancy: Diagnosis, Blood Pressure Goals, and Pharmacotherapy: A Scientific Statement from the American Heart Foundation - PMC
2025 AHA/ACC/AANP/AAPA/ABC/ACCP/ACPM/AGS/AMA/ASPC/NMA/PCNA/SGIM Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines - PubMed
Hypertension in Pregnancy: NICE 2023 Guideline Summary for Specialists
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