Hypertensive disorders in pregnancy are a major cause of maternal, fetal and neonatal morbidity and mortality, both in 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:
- Abruptio placentae.
- Cerebrovascular accident.
- Disseminated intravascular coagulation.
The fetus has an increased risk of:
- Intrauterine growth restriction.
- Intrauterine death.
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 not identified until the latter half of pregnancy:
- Pre-eclampsia: pregnancy-induced hypertension plus proteinuria and/or oedema or both.
- Eclampsia - occurrence of one or more convulsions superimposed on pre-eclampsia. See separate Pre-eclampsia and Eclampsia article.
- 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.
- Use a sitting or semi-reclining position so that the arm to be used is at the level of the heart.
- Do not take the BP in the upper arm with the woman on her side, as this will give falsely lower readings.
- Korotkoff phase 5 measurements should be used for taking the diastolic pressure, except on those rare instances when sounds continue to be heard to 0 mm Hg when Korotkoff phase 4 can be used.
Management depends on the woman's BP, 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:[2, 4]
- Severe headache.
- Visual problems: blurred vision or flashing before the eyes.
- Severe epigastric pain.
- Sudden swelling of the face, hands or feet.
- Hypertension or pre-eclampsia/eclampsia 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; however, 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 separate Pre-eclampsia and Eclampsia article.
- 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 labetalol (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.
White coat hypertension
The phenomenon of patients having high BP when seen in a clinic by their medical carer but normal BP in their work or home environment, is well recognised and referred to as white coat hypertension (WCH). Knowing that WCH exists, there will be a subset of pregnant women diagnosed with gestational hypertension, who will actually have WCH but there is no guidance on how to identify these women. See also Ambulatory Blood Pressure Monitoring article.
- A study of 155 women with high BP diagnosed for the first time during the first half of their pregnancy, found that 50% of them had normal ABPM readings.
- In this study, WCH was diagnosed when awake average ABPM ≤130/80 mm Hg at or prior to 26 weeks gestation and ≤135/85 if after 26 weeks of gestation.
- About 50% of these women continued to have WHC throughout their pregnancy, 40% went on to develop gestational hypertension and 8% developed pre-eclampsia, a lower percentage than in the group who had 'true' hypertension. The women with 'true' hypertension were delivered one week earlier and had babies of lower birth weight, although the caesarean section rate, small-for-gestational-age rates and perinatal mortality were the same in both groups.
- It has been suggested that ABPM is useful in determining whether women with high BP early in pregnancy have 'true' hypertension or WCH. If the latter, pregnancy outcomes appear to be good and unnecessary interventions may be avoided.
- However, a Cochrane review did not find any trial evidence to support the use of ABPM in pregnancy.
- It should be noted that not all ambulatory or automatic BP monitors have been validated in pregnancy and they may underestimate BP.
- It is important when diagnosing high BP in pregnancy to ensure that it is taken several times and in the least stressful environment. Whilst vital not to miss the diagnosis of hypertension in pregnancy, making the diagnosis in error has significant implications for a healthy woman's antenatal care and possibly the timing and mode of delivery.
- 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) is increased in severe hypertension.
- Gestational hypertension: similar risks to normotensive women; however, 40% of those presenting before 34 weeks of gestation will go on to develop pre-eclampsia.
- Hypertensive disorders in pregnancy are an important risk factor for cardiovascular disease in later life. 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.
Dr Hayley Willacy would like to draw your attention to this recent paper looking at the risk of developing hypertension after having had a hypertensive disorder of pregnancy. They found that in a first pregnancy in their 20s, 14% of the women developed hypertension in the first decade post partum, compared with 4% of women with normotensive first pregnancies in their 20s. The corresponding percentages for women with a first pregnancy in their 40s were 32% and 11%, respectively. In the year after delivery, women with a hypertensive disorder of pregnancy had 12-fold to 25-fold higher rates of hypertension than did women with a normotensive pregnancy. Rates in women with a hypertensive disorder of pregnancy were threefold to 10-fold higher 1-10 years post partum and remained twice as high even 20 or more years later.
- Low-dose aspirin: see recommendation in high-risk groups as detailed under 'Management', 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 and references
Hypertension in pregnancy; NICE Quality Standard, July 2013
Bramham K, Nelson-Piercy C, Brown MJ, et al; Postpartum management of hypertension. BMJ. 2013 Feb 25346:f894. doi: 10.1136/bmj.f894.
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 for uncomplicated pregnancies; NICE Clinical Guideline (March 2008, updated 2018)
Hypertension in pregnancy; NICE Clinical Guideline (August 2010, updated 2011)
Brown MA, Mangos G, Davis G, et al; The natural history of white coat hypertension during pregnancy. BJOG. 2005 May112(5):601-6.
Brown MA; Is there a role for ambulatory blood pressure monitoring in pregnancy? Clin Exp Pharmacol Physiol. 2014 Jan41(1):16-21. doi: 10.1111/1440-1681.12106.
Bergel E, Carroli G, Althabe F; Ambulatory versus conventional methods for monitoring blood pressure during pregnancy. Cochrane Database Syst Rev. 2002(2):CD001231.
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 22123(11):1243-62. doi: 10.1161/CIR.0b013e31820faaf8. Epub 2011 Feb 14.
Behrens I, Basit S, Melbye M, et al; Risk of post-pregnancy hypertension in women with a history of hypertensive disorders of pregnancy: nationwide cohort study. BMJ. 2017 Jul 12358:j3078. doi: 10.1136/bmj.j3078.
Hofmeyr GJ, Lawrie TA, Atallah AN, et al; Calcium supplementation during pregnancy for preventing hypertensive disorders and related problems. Cochrane Database Syst Rev. 2010 Aug 48:CD001059.