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Hypertensive disorders in pregnancy are a major cause of maternal, fetal, and neonatal morbidity and mortality in both developing and developed countries. Hypertension is the most common medical problem in pregnancy, complicating up to 15% of pregnancies and accounting for about a quarter of all antenatal admissions in the UK.
Women with hypertension in pregnancy have a higher risk of complications such as:
The fetus has an increased risk of:
Hypertension in pregnancy includes:
- Gestational hypertension - pregnancy-induced hypertension which develops after 20 weeks of gestation and may be either transient hypertension of pregnancy or chronic hypertension identified in the latter half of pregnancy.
- Pre-existing hypertension: is defined as a systolic blood pressure (BP) of 140 mm Hg or greater, and/or a diastolic BP of 90 mm Hg or more, either pre-pregnancy or at booking (before 20 weeks).
- Pre-eclampsia in addition to pre-existing chronic hypertension.
Management depends on the woman's blood pressure, gestational age and blood flow in the placenta. Non-pharmacological management is recommended for many women but is not recommended when there is the presence of associated maternal and fetal risk factors. Non-pharmacological management includes close supervision, limitation of activities, and some bed rest in the left lateral position.
Such symptoms include:
- Severe headache.
- Visual problems: blurred vision or flashing before the eyes.
- Severe epigastric pain.
- Sudden swelling of the face, hands or feet.
Such women are those with:
- Hypertension in a past pregnancy.
- Chronic kidney disease.
- Autoimmune disease (eg, systemic lupus erythematosus (SLE) or antiphospholipid syndrome).
- Diabetes mellitus (both type 1 or 2).
- Chronic hypertension.
- In their first pregnancy.
- Aged ≥40 years.
- Previous pregnancy >10 years ago.
- Body mass index (BMI) of ≥35 kg/m2 at booking.
- Family history of pre-eclampsia.
- Multiple pregnancy.
Patients with pre-existing hypertension who become pregnant
- Review medication and inform the patient of the risks involved with some medications. Those on angiotensin-converting enzyme (ACE) inhibitors or angiotensin-II receptor antagonists (AIIRAs) should be switched from these as soon as possible, as there is an increased risk of congenital abnormalities if these drugs are taken during pregnancy. Ideally this will have been done at a pre-pregnancy counselling session, but if not it should be done as early as possible in the pregnancy. Diuretics should be avoided, as they can reduce the blood flow in the placenta.
- Aim to keep BP lower than 150/100 mm Hg (140/90 mm Hg if there is target organ damage) although do not seek to lower the diastolic level below 80 mm Hg.
- Test for proteinuria regularly - if this shows ≥1+ arrange a spot urinary protein:creatinine ratio or 24-hour urine collection to quantify proteinuria. There is significant proteinuria if urinary protein:creatinine ratio is >30 mg/mmol or 24-hour urine collection has >300 mg protein (treat the patient as for pre-eclampsia - see 'Pre-eclampsia (hypertension with proteinuria and oedema)', below).
- Ultrasound examination is used to assess fetal growth and amniotic fluid volume (with umbilical artery Doppler velocimetry) at 28-30 weeks and 32-34 weeks.
- After delivery - If methyldopa is used - switch back to the pre-pregnancy antihypertensive regime within two days of delivery.
- Assess severity:
- Mild: 140-149/90-99 mm Hg. For patients presenting before 32 weeks (or at high risk of pre-eclampsia), measure BP twice a week; otherwise, measure BP no more often than weekly. Check urine for protein at each visit.
- Moderate: 150-159/100-109 mm Hg. Monitor BP twice a week - start labetolol (alternatives are methyldopa or nifedipine) to keep systolic BP <150 mm Hg and diastolic BP between 80-100 mm Hg. Dip urine for protein at each visit. Arrange initial blood tests for FBC, electrolytes, renal function, and LFTs. Subsequent blood tests are not necessary if there is no proteinuria.
- Severe: ≥160/110 mm Hg. Admit to hospital and treat as for moderate (above) to keep systolic BP <150 mm Hg and diastolic BP between 80-100 mm Hg. Measure BP at least four times a day and check urine for protein daily. Weekly blood tests for FBC, electrolytes, renal function, and LFTs. Check BP and urine twice weekly (and continue weekly blood tests) when discharged (once BP is in the target range).
- Perform ultrasound examination at 34 weeks to assess fetal growth and amniotic fluid volume (with umbilical artery Doppler velocimetry) if mild or moderate gestational hypertension develops before this time. Arrange these tests and cardiotocography urgently whenever severe gestational hypertension is diagnosed.
- After birth, measure BP daily for the first two days after birth, at least once between day three and day five, then as clinically indicated. Continue on antihypertensive medication, but reduce or stop if BP is seen to be falling - particularly if it falls below 130/80 mm Hg. Switch women from methyldopa to an alternative within two days of delivery. Women with mild hypertension not requiring treatment during pregnancy should be started on antihypertensive medication postnatally if their BP is ≥150/100 mm Hg.
Pre-eclampsia (hypertension with proteinuria and oedema)
- Admit and monitor the patient in hospital. Always ask about headache and epigastric pain each time BP is taken, to alert for any indication of progression towards eclampsia.
- Assess severity:
- Mild: 140-149/90-99 mm Hg. Monitor BP at least four times per day. Twice-weekly blood tests for FBC, electrolytes, renal function, and LFTs.
- Moderate: 150-159/100-109 mm Hg or Severe: ≥160/110 mm Hg. Monitor BP at least four times per day. Start labetolol (or alternative) to keep systolic BP <150 mm Hg and diastolic BP between 80-100 mm Hg. Blood tests three times per week.
- Perform ultrasound examination to assess fetal growth and amniotic fluid volume (with umbilical artery Doppler velocimetry) and cardiotocography whenever pre-eclampsia is diagnosed.
- Repeat cardiotocography if there is a change in fetal movements, vaginal bleeding, abdominal pain or a deterioration in maternal condition.
- Pre-eclampsia will usually be managed conservatively (ie without delivery of the baby) until at least 34 weeks. The management plan for delivery (including thresholds for early delivery) will be discussed with the parents on an individual basis and documented in the notes. Patients with mild or moderate pre-eclampsia are usually delivered between 34+0 to 36+6 weeks depending on assessment of risk and availability of a special care baby unit, with fetal monitoring and after a course of corticosteroids to reduce the risk of infant respiratory distress syndrome (if appropriate).
- Signs of complications developing include headache, epigastric pain, papilloedema, hepatic tenderness, signs of clonus (>3 beats), HELLP syndrome (= Haemolysis, EL (elevated liver) enzymes, LP (low platelet) count), platelet count falling (below 100 x 109/L), abnormal liver enzymes (ALT or AST >70 IU/L). Consider anticonvulsants (usually intravenous magnesium sulfate).
- Intrapartum - with mild and moderate hypertension (140/90-159/109 mm Hg), measure BP hourly; with more severe hypertension, measure continually.
- After birth, stop methyldopa (if used) within two days and avoid diuretics if breast-feeding, measuring BP at least four times daily whilst in hospital. Continue to ask about headaches and epigastric pain whenever BP is taken. Measure FBC, LFT and creatinine 72 hours after birth and only repeat after this if abnormal. Step down care (ie to community midwives) when BP is <150/100 mm Hg and blood tests are stable or improving without any pre-eclamptic symptoms.
- Reduce BP treatment if BP falls to <130/80 mm Hg (consider reducing when <140/90 mm Hg).
- Measure BP every 1-2 days for up to two weeks after transfer to community care (or until antihypertensive treatment is stopped). Continue to monitor (ie weekly) and arrange a medical review at two weeks postnatal if still requiring medication. Monitor BP at least until the 6-week check where a urine dip should also be performed (and arrange repeat FBC, creatinine and LFTs unless they have previously returned to normal).
- Hypertensive diseases of pregnancy remain the second leading cause of direct maternal deaths in the UK.
- However, most women with pre-existing mild to moderate hypertension (BP less than 160/110 mm Hg) are at low risk of perinatal complications.
- The risk of complications (eg, pre-eclampsia, placental abruption, impaired fetal growth and premature birth) are increased in severe hypertension.
- Gestational hypertension: similar risks to normotensive women, but 40% of those presenting before 34 weeks of gestation will go on to develop pre-eclampsia.
- Women who develop gestational hypertension or pre-eclampsia are at increased risk of hypertension, cardiovascular disease and stroke in later adult life.
- Hypertensive disorders in pregnancy are an important risk factor for cardiovascular disease in women. Therefore, lifestyle modifications, regular BP control, and control of metabolic factors are recommended after delivery, to avoid complications in subsequent pregnancies and to reduce maternal cardiovascular risk in the future.
- Low-dose aspirin: see recommendation in high-risk groups as detailed under 'Epidemiology', above.
- Calcium supplementation: appears to reduce the risk of high BP in pregnancy, particularly for women at high risk of gestational hypertension and in communities with low dietary calcium intake.
Further reading & references
- Hypertension in pregnancy; NICE Quality Standards (July 2013)
- Hypertension: management of hypertension in adults in primary care; NICE Clinical Guideline (August 2011)
- Management of cardiovascular diseases during pregnancy, European Society of Cardiology (2011)
- Antenatal care; NICE Clinical Guideline (March 2008)
- Hypertension in pregnancy; NICE Clinical Guideline (August 2010)
- Guidelines on diabetes, pre-diabetes and cardiovascular diseases; European Society of Cardiology (2007)
- Mosca L, Benjamin EJ, Berra K, et al; Effectiveness-based guidelines for the prevention of cardiovascular disease in women--2011 update: a guideline from the american heart association. Circulation. 2011 Mar 22;123(11):1243-62. doi: 10.1161/CIR.0b013e31820faaf8. Epub 2011 Feb 14.
- Hofmeyr GJ, Lawrie TA, Atallah AN, et al; Calcium supplementation during pregnancy for preventing hypertensive disorders Cochrane Database Syst Rev. 2010 Aug 4;8:CD001059.
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Dr Colin Tidy
Dr Louise Newson
Dr John Cox