Dr Chris Barry explains how the NICE guideline on hypertension in pregnancy will help management of women at risk and improve referral of affected individuals
- Stop ACE inhibitors, ARBs, and chlorothiazides before conception if possible, changing to a more appropriate drug, and seeking specialist advice
- Pre-eclampsia is a very serious condition that does not always present with signs or symptoms
- Refer immediately if the woman has a diastolic blood pressure over 90 mmHg, and/or proteinuria
- Take a history for risk factors, and offer aspirin from the 12th week of pregnancy where relevant
- Salt restriction is useful in a woman who has hypertension, but not for prevention
- If circumstances force you to treat a pregnant woman who has hypertension, refer to the NICE guideline for the blood pressure levels to aim for—all you need is included in the easy-to-read quick reference guide
- Symptoms can be misleading—always check blood pressure and urine; epigastric pain may be a symptom so don’t be misled by heartburn
- There is no evidence to suggest that most women who are receiving medication should not breastfeed
- If a woman who has previously had hypertension in pregnancy becomes pregnant again, she is at increased risk of recurrence of hypertensive disorders, and should be advised to start aspirin from the 12th week of pregnancy.
ACE=angiotensin-converting enzyme; ARB=angiotensin II receptor blockers
NICE has a reputation, in the lay press at least, for being a ‘watchdog’, imposing strictures on clinical practice; it was most refreshing, therefore, to be part of the Guideline Development Group (GDG) that produced the guideline on Hypertension in pregnancy: the management of hypertensive disorders during pregnancy.1,2 Our multi-professional group comprised representation from the fields of obstetrics, anaesthetics, neonatology, midwifery, general practice (myself), and lay representatives, including a trustee of ‘Action on Pre-eclampsia’. The GDG worked together with mutual respect—all views were listened to, and the researchers and analysts from the National Collaborating Centre for Women’s and Children’s Health gave us comprehensive and clear information with which to work.
Hypertension in pregnancy is defined as a diastolic blood pressure of ?90 mmHg on two occasions more than 4 hours apart, or a single reading over 100 mmHg.2 Although hypertensive disorders in pregnancy should not be managed in primary care, it is vital for GPs to be aware of the three different types, not only for their management, but their risk factors, prevention, follow up, and how and where to be vigilant when a patient who is pregnant presents. Pre-eclampsia is a leading cause of maternal and fetal morbidity and death, and a significant number of affected women present to their primary care physician.2
The three hypertensive disorders are:1,2
- chronic hypertension—occurs in a woman who is already hypertensive when she becomes pregnant. This group is small, but important because some antihypertensive drugs are teratogenic, and should be stopped or changed, before pregnancy if possible
- gestational hypertension—new hypertension
- pre-eclampsia—new hypertension with the presence of proteinuria.
Risk factors and pre-conceptual advice
Women who are at high risk of pre-eclampsia should be advised to take aspirin 75 mg daily (there is no marketing authorisation for this indication) from the 12th week of pregnancy until birth. Women are at high risk if they have:1,2
- had hypertensive disease during a previous pregnancy
- chronic renal disease
- autoimmune disease such as systemic lupus erythematosis or antiphospholipid syndrome
- diabetes (type 1 or type 2)
- chronic hypertension.
The NICE clinical guideline recommends that women with more than one moderate risk factor for pre-eclampsia should also receive aspirin 75 mg daily from the 12th week of pregnancy until birth. Moderate risk factors include:1
- first pregnancy
- interval since last pregnancy of >10 years
- aged ?40 years
- body mass index of ?35 kg/m2
- family history of pre-eclampsia
- multiple pregnancy.
Hypertensive women taking chlorothiazide diuretics, angiotensin-converting enzyme inhibitors, or angiotensin receptor blockers should receive an alternative drug, preferably before conception, and immediately if they are taking them when they present with their pregnancy, as these drugs are teratogenic.
Discussions about antihypertensives should take place between the woman and the healthcare professional managing her hypertension, and advice should be given to all women with hypertension who are of childbearing age. This advice should be given by the woman’s GP or specialist if she is under specialist care for her hypertension. There is no evidence that other antihypertensives carry any risk,1 but the only antihypertensive drug licensed for use in pregnancy is labetalol.2 Treatment should aim to keep the blood pressure below 150/100 mmHg (see below), but obviously all pregnant women who are hypertensive should be under specialist care.1,2
There is no evidence that other interventions improve outcomes in hypertension in pregnancy. Drugs such as diuretics (refer to the guideline for a full list) should not be used; the use of nutritional supplements such as antioxidants, fish oils, and garlic has no evidence base and cannot be recommended. Likewise, salt restriction is not indicated for the prevention of hypertension in pregnancy, but if a woman becomes hypertensive she should restrict her dietary sodium. Other lifestyle advice is the same as for a normal pregnancy (i.e. live normally, with the usual things to avoid).1
Proteinuria and pre-eclampsia
The management of hypertensive disorders in pregnancy varies according to the form that is present, but all women with hypertension should be under specialist care and they will need to be seen more frequently than standard. Women who develop pre-eclampsia should be managed in hospital while chronic and gestational hypertension can be managed outside this setting.
The presence of significant proteinuria—meaning more than 300 mg protein in a 24-hour collection—carries with it very important consequences. In primary care, a dipstick is used at each visit to test for proteinuria; this test has relatively low sensitivity and specificity. A formal diagnosis of pre-eclampsia requires re-testing of the urine (in secondary care) with an automated dipstick device or by performing a spot urinary protein/creatinine ratio (PCR).1,2 This may obviate the need for a 24-hour specimen, although this test, if properly conducted, remains the gold standard. If an automated dipstick device gives a reading of 1+ or more, the result should be validated by one of the two latter tests; some units may decide to do the PCR only.
Once pre-eclampsia has been diagnosed the test does not need to be repeated and these women should be under specialist care.
The NICE quick reference guide contains several algorithms covering the management of the various types and severities of hypertension in pregnancy.4 General practitioners should refer if the blood pressure is above the limits set in the algorithms or if there is proteinuria. The algorithms also set out upper and lower limits for blood pressure, with an optimal range of values, depending on the condition.3
The presentation of pre-eclampsia may be subtle. The classic symptoms of headache, visual disturbance, vomiting, oedema and/or epigastric pain1 are very non-specific and can be absent. So always check the woman’s blood pressure and urine!
Timing of birth
The NICE guideline includes recommendations about the various forms of monitoring in pregnancy and timing of birth in women with pre-eclampsia. The aim is to minimise prematurity at the same time as decreasing risk to mother and baby. This, of course, may be a delicate balance. General practitioners will not need to be familiar with the details, but a patient may want to discuss the pros and cons so it is useful to be aware that the NICE guideline contains the necessary information.1
Women who have had pre-eclampsia should have their blood pressure measured until they are no longer taking antihypertensive treatment and have no hypertension. Women who have been given methyldopa as part of their treatment should stop it within 2 days of birth, and change it to a conventional drug.1,2
Before being discharged from hospital, all women with gestational hypertension or pre-eclampsia should be advised that they are at increased risk of developing hypertension or other related conditions (such as renal failure and cardiovascular disease) in later life. If a woman who has had pre-eclampsia is normotensive at the 6–8 week postnatal visit and has no proteinuria, the risk of developing renal disease is very low indeed, and no further checks need to be made.1
However, the risk of developing either the gestational or pre-eclampsia form of hypertension in a subsequent pregnancy will have increased to around 1 in 8, or even more if the woman previously had severe pre-eclampsia or HELLP (hemolytic anaemia, elevated liver enzymes and low platelet count)syndrome, in which case the risk will now be 1 in 2.1
All women who have had any form of hypertension in pregnancy should have been discharged from secondary care with a care plan that specifies who does what in terms of monitoring and treatment.
The NICE guideline also covers long-term follow up and advice in relation to cardiovascular and end-stage kidney disease risk, and risk of recurrence of hypertensive disorders of pregnancy.1,2
Oddly enough, breastfeeding is not recommended for women still on labetalol; indeed it is a contraindication in the product leaflets for any antihypertensive. However, a review of the evidence has led the GDG to the conclusion that there are no known adverse effects for labetalol, nifedipine, enalapril, captopril, atenolol, metoprolol, or the thiazides although some of these cautions apply to pre-term infants only.1,2 Verapamil and propranolol are present in breast milk but in such tiny quantities that they are unlikely to cause any adverse effects.
There is insufficient evidence of safety (not quite the same thing) for the angiotensin II receptor blockers, amlodipine, or the other angiotensin-converting enzyme inhibitors (other than enalapril and captopril). Details of all these data can be found in the full guideline and there is a table summarising the studies that have evaluated the safety of antihypertensives commonly used during breastfeeding. As a result of the uncertainties in the evidence, the GDG has recommended research into the presence and effects, if any, of antihypertensive drugs in breast milk.2
The main relevance to GPs of this NICE guideline is to be aware of the possibility of hypertension in any of its three forms. They should check blood pressure, urine test, and refer any pregnant woman who develops hypertension. The speed of referral will depend on the severity of the condition and the presence of proteinuria, but it is important that a woman with possible pre-eclampsia should be referred immediately. Aspirin 75 mg daily should be offered from the 12th week of pregnancy to women at increased risk of developing hypertension.
This article is based on work undertaken by the National Collaborating Centre for Women’s and Children’s Health, which received funding from the National Institute for Health and Care Excellence. The views expressed in this publication are those of the author and not necessarily those of the Institute.
NICE has developed the following tools to support implementation of Clinical Guideline 107 on Hypertension in pregnancy: The management of hypertensive disorders during pregnancy. The tools are now available to download from the NICE website: www.nice.org.uk
Audit support has been developed to support the implementation of this guideline. The aim is to help NHS organisations with the audit process, to ensure that practice is in line with the NICE recommendations. The audit support is based on the key recommendations of the guidance and includes criteria and data collection tools.
Baseline assessment tool
The baseline assessment tool is an Excel spreadsheet that can be used by organisations to identify if they are in line with practice recommended in NICE guidance and to help them plan activity that will help them meet the recommendations.
A costing report and local cost template for the guideline have been produced:
The slides provide a framework for discussing the NICE guideline with a variety of audiences and can assist in local dissemination. This information does not supersede or replace the guidance itself.
- The NICE guideline is easy to follow and local guidance should be reviewed to urgently accommodate its advice and standards
- This guidance should be built in to service specifications and contracts for local maternity care providers
- A retrospective audit of women presenting with hypertension in pregnancy against this guidance may identify specific learning needs and gaps in service delivery
- Commissioners should consider appropriate educational input to GPs and community midwives in order to raise awareness of the guidance
- Local production of a patient leaflet explaining the rationale for off-licence use of aspirin as prophylaxis would be useful for clinicians to issue.
- National Institute for Health and Care Excellence. Hypertension in pregnancy: The management of hypertensive disorders during pregnancy. Clinical Guideline 107. London: NICE, 2010. Available at: www.nice.org.uk/guidance/CG107
- National Collaborating Centre for Women’s and Children’s Health. Hypertension in pregnancy: The management of hypertensive disorders during pregnancy. London: RCOG, 2010. Available at: www.nice.org.uk/guidance/CG107
- British National Formulary. BNF 60—September 2010. London: BMJ Group, Pharmaceutical Press, 2010.
- National Institute for Health and Care Excellence. Hypertension in pregnancy: The management of hypertensive disorders during pregnancy. Quick reference guide. Clinical Guideline 107. London: NICE, 2010. Available at: www.nice.org.uk/guidance/CG1077 G