Hypertension in Pregnancy

Hypertension in pregnancy includes:¹

• Pre-existing hypertension: is defined as a systolic blood pressure of 140 mmHg or greater, and/or a diastolic blood pressure of 90 mmHg or more, either pre-pregnancy or at booking (before 20 weeks).
• Pregnancy-induced hypertension (gestational hypertension): this develops after 20 weeks' gestation and may be either transient hypertension of pregnancy or chronic hypertension identified in the latter half of pregnancy.
• Pre-eclampsia: pregnancy-induced hypertension in association with proteinuria and/or oedema or both. See separate article called 'Pre-eclampsia and eclampsia'.
• Pre-eclampsia in addition to pre-existing chronic hypertension.

• Chronic hypertension affects 1 to 5% of pregnancies.²
• Pregnancy-induced hypertension (now preferably known as gestational hypertension) affects 5 to 10% of all pregnancies. It is more common in first pregnancies (up to 25%).²

• Hypertension is diagnosed if systolic BP is greater than or equal to 140 mmHg or diastolic BP is greater than or equal to 90 mmHg.
• Most women will be asymptomatic and so routine monitoring of blood pressure and urine for proteinuria. The frequency of monitoring should be determined by local guidelines and the NICE guidelines for routine antenatal care.³
• The symptoms for pre-eclampsia and eclampsia are discussed in the separate article (above). Click here for details.

• Secondary hypertension (e.g. phaeochromocytoma which may cause sudden death in pregnancy) is rare in pregnancy
• Other gastrointestinal or renal disorders (e.g. pancreatitis, appendicitis, glomerulonephritis)
• Acute fatty liver of pregnancy
• Systemic lupus erythematosus
• Autoimmune thrombocytopenia purpura
• Encephalitis
• Cerebral venous thrombosis
• Cerebral haemorrhage

• Urinalysis for proteinuria; send urine for culture and sensitivities.
• Initial blood tests include full blood count, urea and electrolytes, serum urate and liver function tests - these are usually done in secondary care.
• Fetal monitoring.
• Investigations as indicated for possible secondary hypertension or in consideration of differential diagnoses.

• Women with pre-existing hypertension or a booking diastolic blood pressure of 90 mmHg or more should be referred early in pregnancy for specialist care.
• Women with new proteinuria without hypertension after 20 weeks:
  • 1 on dipstick: repeat pre-eclampsia assessment in the community within 1 week
  • 2 or more on dipstick: refer for hospital assessment within 48 hours
  • 1 or more on dipstick with epigastric pain, vomiting, headache, visual disturbances, reduced fetal movements, or small for gestational age infant: refer for same-day hospital assessment
• Women with new hypertension without proteinuria after 20 weeks:
  • Diastolic BP 90-99 mmHg: refer for hospital assessment within 48 hours
  • Diastolic BP 90-99 mmHg with epigastric pain, vomiting, headache, visual disturbances, reduced fetal movements, or small for gestational age infant: refer for same-day hospital assessment
  • Diastolic BP 100 mmHg or greater: refer for same-day hospital assessment
  • Systolic BP 160-169 mmHg: refer for same-day hospital assessment (even if diastolic below 90 mmHg)
  • Systolic BP 170 mmHg or greater: arrange immediate admission for treatment of systolic BP (even if diastolic pressure is below 90 mmHg
• Women with new hypertension and new proteinuria after 20 weeks:
  • Diastolic BP 90 mmHg or greater and new proteinuria 1 or more on dipstick: refer for same-day hospital assessment
  • Diastolic BP 110 mmHg or greater and new proteinuria 1 or more on dipstick: arrange immediate admission
  • Systolic BP 160-169 mmHg and new proteinuria 1 or more on dipstick: refer for same-day hospital assessment (even if diastolic pressure is less than 90 mmHg)
  • Systolic BP 170 mmHg or greater and new proteinuria 1 or more on dipstick: arrange immediate admission for treatment of systolic BP (even if diastolic pressure is less than 90 mmHg)
  • Diastolic BP 90 mmHg or greater and new proteinuria 1 or more on dipstick and epigastric pain, vomiting, headache, visual disturbances, reduced fetal movements, or small for gestational age infant: arrange immediate admission

All pregnant women should receive antenatal education so that they are aware of the symptoms associated with pre-eclampsia, its importance, and the need to obtain medical advice.

Gestational hypertension

It remains unclear whether antihypertensive drug therapy for mild to moderate hypertension during pregnancy is worthwhile.⁵ Severe hypertension always requires treatment. Antihypertensive treatment is recommended if the systolic pressure exceeds 160 mmHg, or the diastolic exceeds 110 mmHg.
General measures:

• Careful monitoring to detect the onset of pre-eclampsia.
• Bed rest and stress management have not been shown to reduce the risk of pre-eclampsia.
• Alcohol and tobacco use should be even more strongly discouraged.

• Methyldopa, labetalol, nifedipine and hydralazine are most commonly used.^6,7 Methyldopa is usually the drug of choice, labetalol is often used as a second-line agent, and nifedipine is a third-line drug to methyldopa and labetalol.¹
• ACE inhibitors and angiotensin-receptor antagonists should be avoided as they may be associated with intrauterine death.⁸
• Low-dose thiazides in women with pre-existing hypertension may be continued but generally diuretics are little used.
• Pre-pregnancy counselling in women with pre-existing hypertension should include switching to a recommended drug regime during the pregnancy.

Management of severe hypertension in pregnancy

Described as 160 mmHg or greater systolic, or diastolic greater than 109 mmHg or both.

• Requires admission to a specialist unit.
• If urgent treatment required, use of labetolol, magnesium sulfate, intravenous hydralazine, or oral or sublingual nifedipine.
• Anticonvulsant therapy may be initiated to prevent and treat seizures.
• Delivery after stabilisation best option but need to weigh up disadvantages for very premature babies.

• Pregnant women with chronic hypertension are at increased risk of pre-eclampsia and placental abruption.

• Hypertensive diseases of pregnancy remain the second leading cause of direct maternal deaths in the UK.⁹
• Most women with pre-existing mild to moderate hypertension (BP less than 160/110 mmHg) are at low risk of perinatal complications.¹
• The risk of complications (e.g. 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' gestation will go on to develop pre-eclampsia.
• Hypertension and/or proteinuria is the leading single identifiable risk factor in pregnancy associated with stillbirth.

• Low-dose aspirin: not used routinely, but may be indicated in those with history of early onset pre-eclampsia in a previous pregnancy.
• Calcium supplementation: appears to reduce the risk of high blood pressure in pregnancy, particularly for women at high risk of gestational hypertension and in communities with low-dietary calcium intake.¹⁰